One change
Count tokens in a Message
api/messages/count_tokens
Nearest release: v2.1.245, published an hour after this site recorded the change. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.
api/messages/count_tokens Changed · +303 / -380 lines
# Count tokens in a Message ## Headers ## Body parameters ## Returns ## Example ### Response (200) ## Count tokens in a Message ### Header Parameters ### Body Parameters ### Returns ### Example #### Response
The two sides of this change are too far apart to line up, so this is the differ's own diff of it.
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---- -title: Count tokens in a Message -url: https://platform.claude.com/docs/en/api/messages/count_tokens ---- - -## Count tokens in a Message - -**post** `/v1/messages/count_tokens` +# Count tokens in a Message + +**POST** `/v1/messages/count_tokens` Count the number of tokens in a Message.
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Learn more about token counting in our [user guide](https://platform.claude.com/docs/en/build-with-claude/token-counting) -### Header Parameters +## Headers - `"anthropic-user-profile-id": optional string` The user profile ID to attribute this request to. Use when acting on behalf of a party other than your organization. Requires the `user-profiles` beta header. -### Body Parameters +## Body parameters - `messages: array of MessageParam`
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- `array of ContentBlockParam` - - `TextBlockParam object { text, type, cache_control, citations }` + - `TextBlockParam object` - `text: string` + minLength: 1 + - `type: "text"` - - `"text"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block. - `type: "ephemeral"` - - - `"ephemeral"` - `ttl: optional "5m" or "1h"`
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- `citations: optional array of TextCitationParam or null` - - `CitationCharLocationParam object { cited_text, document_index, document_title, 3 more }` + - `CitationCharLocationParam object` - `cited_text: string` - `document_index: number` + minimum: 0 + - `document_title: string or null` + maxLength: 500, minLength: 1 + - `end_char_index: number` - `start_char_index: number` + minimum: 0 + - `type: "char_location"` - - `"char_location"` - - - `CitationPageLocationParam object { cited_text, document_index, document_title, 3 more }` + - `CitationPageLocationParam object` - `cited_text: string` - `document_index: number` + minimum: 0 + - `document_title: string or null` + maxLength: 500, minLength: 1 + - `end_page_number: number` - `start_page_number: number` + minimum: 1 + - `type: "page_location"` - - `"page_location"` - - - `CitationContentBlockLocationParam object { cited_text, document_index, document_title, 3 more }` + - `CitationContentBlockLocationParam object` - `cited_text: string`
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- `document_index: number` + minimum: 0 + - `document_title: string or null` + maxLength: 500, minLength: 1 + - `end_block_index: number` Exclusive 0-based end index of the cited block range in the source's `content` array.
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0-based index of the first cited block in the source's `content` array. + minimum: 0 + - `type: "content_block_location"` - - `"content_block_location"` - - - `CitationWebSearchResultLocationParam object { cited_text, encrypted_index, title, 2 more }` + - `CitationWebSearchResultLocationParam object` - `cited_text: string`
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- `title: string or null` + maxLength: 512, minLength: 1 + - `type: "web_search_result_location"` - - `"web_search_result_location"` - - `url: string` - - `CitationSearchResultLocationParam object { cited_text, end_block_index, search_result_index, 4 more }` + minLength: 1 + + - `CitationSearchResultLocationParam object` - `cited_text: string`
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Counted separately from `document_index`; server-side web search results are not included in this count. + minimum: 0 + - `source: string` - `start_block_index: number` 0-based index of the first cited block in the source's `content` array. + minimum: 0 + - `title: string or null` - `type: "search_result_location"` - - `"search_result_location"` - - - `ImageBlockParam object { source, type, cache_control, transformations }` + - `ImageBlockParam object` - `source: Base64ImageSource or URLImageSource or FileImageSource` - - `Base64ImageSource object { data, media_type, type }` + - `Base64ImageSource object` - `data: string` + format: byte + - `media_type: "image/jpeg" or "image/png" or "image/gif" or "image/webp"` - `"image/jpeg"`
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- `type: "base64"` - - `"base64"` - - - `URLImageSource object { type, url }` + - `URLImageSource object` - `type: "url"` - - `"url"` - - `url: string` - - `FileImageSource object { file_id, type }` + - `FileImageSource object` - `file_id: string` - `type: "file"` - - `"file"` - - `type: "image"` - - `"image"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block.
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- `"error"` - - `DocumentBlockParam object { source, type, cache_control, 3 more }` + - `DocumentBlockParam object` - `source: Base64PDFSource or PlainTextSource or ContentBlockSource or 2 more` - - `Base64PDFSource object { data, media_type, type }` + - `Base64PDFSource object` - `data: string` + format: byte + - `media_type: "application/pdf"` - - `"application/pdf"` - - `type: "base64"` - - `"base64"` - - - `PlainTextSource object { data, media_type, type }` + - `PlainTextSource object` - `data: string` - `media_type: "text/plain"` - - `"text/plain"` - - `type: "text"` - - `"text"` - - - `ContentBlockSource object { content, type }` + - `ContentBlockSource object` - `content: string or array of ContentBlockSourceContent`
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- `ContentBlockSourceContent = array of ContentBlockSourceContent` - - `TextBlockParam object { text, type, cache_control, citations }` - - - `ImageBlockParam object { source, type, cache_control, transformations }` + - `TextBlockParam object` + + - `ImageBlockParam object` - `type: "content"` - - `"content"` - - - `URLPDFSource object { type, url }` + - `URLPDFSource object` - `type: "url"` - - `"url"` - - `url: string` - - `FileDocumentSource object { file_id, type }` + - `FileDocumentSource object` - `file_id: string` - `type: "file"` - - `"file"` - - `type: "document"` - - `"document"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block.
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- `context: optional string or null` + minLength: 1 + - `title: optional string or null` - - `SearchResultBlockParam object { content, source, title, 3 more }` + maxLength: 500, minLength: 1 + + - `SearchResultBlockParam object` - `content: array of TextBlockParam` - `text: string` + minLength: 1 + - `type: "text"` - `cache_control: optional CacheControlEphemeral or null`
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- `type: "search_result"` - - `"search_result"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block. - `citations: optional CitationsConfigParam` - - `ThinkingBlockParam object { signature, thinking, type }` + - `ThinkingBlockParam object` - `signature: string`
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- `type: "thinking"` - - `"thinking"` - - - `RedactedThinkingBlockParam object { data, type }` + - `RedactedThinkingBlockParam object` - `data: string`
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- `type: "redacted_thinking"` - - `"redacted_thinking"` - - - `ToolUseBlockParam object { id, input, name, 4 more }` + - `ToolUseBlockParam object` - `id: string` + pattern: ^[a-zA-Z0-9_-]+$ + - `input: map[unknown]` - `name: string` + maxLength: 200, minLength: 1 + - `type: "tool_use"` - - `"tool_use"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block.
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Tool invocation directly from the model. - - `DirectCaller object { type }` + - `DirectCaller object` Tool invocation directly from the model. - `type: "direct"` - - `"direct"` - - - `ServerToolCaller object { tool_id, type }` + - `ServerToolCaller object` Tool invocation generated by a server-side tool. - `tool_id: string` + pattern: ^srvtoolu_[a-zA-Z0-9_]+$ + - `type: "code_execution_20250825"` - - `"code_execution_20250825"` - - - `ServerToolCaller20260120 object { tool_id, type }` + - `ServerToolCaller20260120 object` - `tool_id: string` + pattern: ^srvtoolu_[a-zA-Z0-9_]+$ + - `type: "code_execution_20260120"` - - `"code_execution_20260120"` - - `toolset_name: optional string or null` For a toolset member tool_use, the toolset family this member belongs to. - - `ToolResultBlockParam object { tool_use_id, type, cache_control, 3 more }` + maxLength: 64, minLength: 1, pattern: ^[a-zA-Z0-9_-]+$ + + - `ToolResultBlockParam object` - `tool_use_id: string` + pattern: ^[a-zA-Z0-9_-]+$ + - `type: "tool_result"` - - `"tool_result"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block.
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- `array of TextBlockParam or ImageBlockParam or SearchResultBlockParam or 3 more` - - `TextBlockParam object { text, type, cache_control, citations }` - - - `ImageBlockParam object { source, type, cache_control, transformations }` - - - `SearchResultBlockParam object { content, source, title, 3 more }` - - - `DocumentBlockParam object { source, type, cache_control, 3 more }` - - - `ToolReferenceBlockParam object { tool_name, type, cache_control }` + - `TextBlockParam object` + + - `ImageBlockParam object` + + - `SearchResultBlockParam object` + + - `DocumentBlockParam object` + + - `ToolReferenceBlockParam object` Tool reference block that can be included in tool_result content. - `tool_name: string` + maxLength: 256, minLength: 1, pattern: ^[a-zA-Z0-9_-]{1,256}$ + - `type: "tool_reference"` - - `"tool_reference"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block. - - `BrowserStateBlockParam object { tabs, type, cache_control, state_changes }` + - `BrowserStateBlockParam object` The caller's browser state after a browser toolset member call — the full inventory of open tabs, which tab is active, and any side
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All tabs open in the browser after this call — the full inventory, not a delta. May be empty. Whenever non-empty, exactly one entry carries `active: true`. + maxItems: 100 + - `tab_id: string` The caller-assigned identifier for this tab, unique within the inventory. + maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$ + - `title: string` The title of the page the tab is showing. May be empty. + maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$ + - `url: string` The URL of the page the tab is showing. May be empty. + maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$ + - `active: optional boolean` Whether this tab is the active tab after this call. Whenever `tabs` is non-empty, exactly one entry is marked `active: true`. - `type: "browser_state"` - - `"browser_state"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block.
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Tabs opened and download state changes during this call. "Nothing to report" is expressed by omitting the field, never by an empty list. - - `BrowserStateChangeTabOpened object { tab_id, type }` + maxItems: 200, minItems: 1 + + - `BrowserStateChangeTabOpened object` A tab this call's execution opened that remains open at its end — the creation delta of the `tabs` inventory, not an event log.
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The `tab_id` of the opened tab, present in `tabs`. + maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$ + - `type: "tab_opened"` - - `"tab_opened"` - - - `BrowserStateChangeDownloadStarted object { download_id, type, url }` + - `BrowserStateChangeDownloadStarted object` A file download that started during this call.
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The caller-assigned identifier for this download, stable across the state changes reporting it. + maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$ + - `type: "download_started"` - - `"download_started"` - - `url: string` The final post-redirect URL the download was served from. - - `BrowserStateChangeDownloadCompleted object { download_id, type, url, 2 more }` + maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$ + + - `BrowserStateChangeDownloadCompleted object` A file download that finished during this call, reported with the same `download_id` as its `download_started` — or without a prior
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The caller-assigned identifier for this download, stable across the state changes reporting it. + maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$ + - `type: "download_completed"` - - `"download_completed"` - - `url: string` The final post-redirect URL the download was served from. + maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$ + - `path: optional string or null` Where the executor saved the file, on the executor's filesystem. Only included when another tool in the same environment can read the file at that path. + pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$, maxLength: 4096 + - `size_bytes: optional number or null` The completed download's size. - - `BrowserStateChangeDownloadFailed object { download_id, type, url, error }` + minimum: 0 + + - `BrowserStateChangeDownloadFailed object` A file download that failed — or was cancelled — during this call.
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The caller-assigned identifier for this download, stable across the state changes reporting it. + maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$ + - `type: "download_failed"` - - `"download_failed"` - - `url: string` The final post-redirect URL the download was served from. + maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$ + - `error: optional string or null` The failure or cancellation detail, when known. + pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$, maxLength: 4096 + - `is_error: optional boolean` - `toolset_name: optional string or null` For a toolset member tool_result, the toolset family of the paired tool_use. - - `ServerToolUseBlockParam object { id, input, name, 3 more }` + maxLength: 64, minLength: 1, pattern: ^[a-zA-Z0-9_-]+$ + + - `ServerToolUseBlockParam object` - `id: string` + pattern: ^srvtoolu_[a-zA-Z0-9_]+$ + - `input: map[unknown]` - `name: "web_search" or "web_fetch" or "code_execution" or 4 more`
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- `type: "server_tool_use"` - - `"server_tool_use"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block.
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Tool invocation directly from the model. - - `DirectCaller object { type }` + - `DirectCaller object` Tool invocation directly from the model. - - `ServerToolCaller object { tool_id, type }` + - `ServerToolCaller object` Tool invocation generated by a server-side tool. - - `ServerToolCaller20260120 object { tool_id, type }` - - - `WebSearchToolResultBlockParam object { content, tool_use_id, type, 2 more }` + - `ServerToolCaller20260120 object` + + - `WebSearchToolResultBlockParam object` - `content: WebSearchToolResultBlockParamContent`
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- `type: "web_search_result"` - - `"web_search_result"` - - `url: string` - `page_age: optional string or null` - - `WebSearchToolRequestError object { error_code, type }` + - `WebSearchToolRequestError object` - `error_code: WebSearchToolResultErrorCode`
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- `type: "web_search_tool_result_error"` - - `"web_search_tool_result_error"` - - `tool_use_id: string` + pattern: ^srvtoolu_[a-zA-Z0-9_]+$ + - `type: "web_search_tool_result"` - - `"web_search_tool_result"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block.
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Tool invocation directly from the model. - - `DirectCaller object { type }` + - `DirectCaller object` Tool invocation directly from the model. - - `ServerToolCaller object { tool_id, type }` + - `ServerToolCaller object` Tool invocation generated by a server-side tool. - - `ServerToolCaller20260120 object { tool_id, type }` - - - `WebFetchToolResultBlockParam object { content, tool_use_id, type, 2 more }` + - `ServerToolCaller20260120 object` + + - `WebFetchToolResultBlockParam object` - `content: WebFetchToolResultErrorBlockParam or WebFetchBlockParam` - - `WebFetchToolResultErrorBlockParam object { error_code, type }` + - `WebFetchToolResultErrorBlockParam object` - `error_code: WebFetchToolResultErrorCode`
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- `type: "web_fetch_tool_result_error"` - - `"web_fetch_tool_result_error"` - - - `WebFetchBlockParam object { content, type, url, retrieved_at }` + - `WebFetchBlockParam object` - `content: DocumentBlockParam` - `type: "web_fetch_result"` - - `"web_fetch_result"` - - `url: string` Fetched content URL
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- `tool_use_id: string` + pattern: ^srvtoolu_[a-zA-Z0-9_]+$ + - `type: "web_fetch_tool_result"` - - `"web_fetch_tool_result"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block.
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Tool invocation directly from the model. - - `DirectCaller object { type }` + - `DirectCaller object` Tool invocation directly from the model. - - `ServerToolCaller object { tool_id, type }` + - `ServerToolCaller object` Tool invocation generated by a server-side tool. - - `ServerToolCaller20260120 object { tool_id, type }` - - - `CodeExecutionToolResultBlockParam object { content, tool_use_id, type, cache_control }` + - `ServerToolCaller20260120 object` + + - `CodeExecutionToolResultBlockParam object` - `content: CodeExecutionToolResultBlockParamContent` Code execution result with encrypted stdout for PFC + web_search results. - - `CodeExecutionToolResultErrorParam object { error_code, type }` + - `CodeExecutionToolResultErrorParam object` - `error_code: CodeExecutionToolResultErrorCode`
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- `type: "code_execution_tool_result_error"` - - `"code_execution_tool_result_error"` - - - `CodeExecutionResultBlockParam object { content, return_code, stderr, 2 more }` + - `CodeExecutionResultBlockParam object` - `content: array of CodeExecutionOutputBlockParam`
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- `type: "code_execution_output"` - - `"code_execution_output"` - - `return_code: number` - `stderr: string`
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- `type: "code_execution_result"` - - `"code_execution_result"` - - - `EncryptedCodeExecutionResultBlockParam object { content, encrypted_stdout, return_code, 2 more }` + - `EncryptedCodeExecutionResultBlockParam object` Code execution result with encrypted stdout for PFC + web_search results.
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- `type: "encrypted_code_execution_result"` - - `"encrypted_code_execution_result"` - - `tool_use_id: string` + pattern: ^srvtoolu_[a-zA-Z0-9_]+$ + - `type: "code_execution_tool_result"` - - `"code_execution_tool_result"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block. - - `BashCodeExecutionToolResultBlockParam object { content, tool_use_id, type, cache_control }` + - `BashCodeExecutionToolResultBlockParam object` - `content: BashCodeExecutionToolResultErrorParam or BashCodeExecutionResultBlockParam` - - `BashCodeExecutionToolResultErrorParam object { error_code, type }` + - `BashCodeExecutionToolResultErrorParam object` - `error_code: BashCodeExecutionToolResultErrorCode`
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- `type: "bash_code_execution_tool_result_error"` - - `"bash_code_execution_tool_result_error"` - - - `BashCodeExecutionResultBlockParam object { content, return_code, stderr, 2 more }` + - `BashCodeExecutionResultBlockParam object` - `content: array of BashCodeExecutionOutputBlockParam`
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- `type: "bash_code_execution_output"` - - `"bash_code_execution_output"` - - `return_code: number` - `stderr: string`
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- `type: "bash_code_execution_result"` - - `"bash_code_execution_result"` - - `tool_use_id: string` + pattern: ^srvtoolu_[a-zA-Z0-9_]+$ + - `type: "bash_code_execution_tool_result"` - - `"bash_code_execution_tool_result"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block. - - `TextEditorCodeExecutionToolResultBlockParam object { content, tool_use_id, type, cache_control }` + - `TextEditorCodeExecutionToolResultBlockParam object` - `content: TextEditorCodeExecutionToolResultErrorParam or TextEditorCodeExecutionViewResultBlockParam or TextEditorCodeExecutionCreateResultBlockParam or TextEditorCodeExecutionStrReplaceResultBlockParam` - - `TextEditorCodeExecutionToolResultErrorParam object { error_code, type, error_message }` + - `TextEditorCodeExecutionToolResultErrorParam object` - `error_code: TextEditorCodeExecutionToolResultErrorCode`
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- `type: "text_editor_code_execution_tool_result_error"` - - `"text_editor_code_execution_tool_result_error"` - - `error_message: optional string or null` - - `TextEditorCodeExecutionViewResultBlockParam object { content, file_type, type, 3 more }` + - `TextEditorCodeExecutionViewResultBlockParam object` - `content: string`
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- `type: "text_editor_code_execution_view_result"` - - `"text_editor_code_execution_view_result"` - - `num_lines: optional number or null` - `start_line: optional number or null` - `total_lines: optional number or null` - - `TextEditorCodeExecutionCreateResultBlockParam object { is_file_update, type }` + - `TextEditorCodeExecutionCreateResultBlockParam object` - `is_file_update: boolean` - `type: "text_editor_code_execution_create_result"` - - `"text_editor_code_execution_create_result"` - - - `TextEditorCodeExecutionStrReplaceResultBlockParam object { type, lines, new_lines, 3 more }` + - `TextEditorCodeExecutionStrReplaceResultBlockParam object` - `type: "text_editor_code_execution_str_replace_result"` - - `"text_editor_code_execution_str_replace_result"` - - `lines: optional array of string or null` - `new_lines: optional number or null`
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- `tool_use_id: string` + pattern: ^srvtoolu_[a-zA-Z0-9_]+$ + - `type: "text_editor_code_execution_tool_result"` - - `"text_editor_code_execution_tool_result"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block. - - `ToolSearchToolResultBlockParam object { content, tool_use_id, type, cache_control }` + - `ToolSearchToolResultBlockParam object` - `content: ToolSearchToolResultErrorParam or ToolSearchToolSearchResultBlockParam` - - `ToolSearchToolResultErrorParam object { error_code, type, error_message }` + - `ToolSearchToolResultErrorParam object` - `error_code: ToolSearchToolResultErrorCode`
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- `type: "tool_search_tool_result_error"` - - `"tool_search_tool_result_error"` - - `error_message: optional string or null` - - `ToolSearchToolSearchResultBlockParam object { tool_references, type }` + - `ToolSearchToolSearchResultBlockParam object` - `tool_references: array of ToolReferenceBlockParam` - `tool_name: string` + maxLength: 256, minLength: 1, pattern: ^[a-zA-Z0-9_-]{1,256}$ + - `type: "tool_reference"` - `cache_control: optional CacheControlEphemeral or null`
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- `type: "tool_search_tool_search_result"` - - `"tool_search_tool_search_result"` - - `tool_use_id: string` + pattern: ^srvtoolu_[a-zA-Z0-9_]+$ + - `type: "tool_search_tool_result"` - - `"tool_search_tool_result"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block. - - `ContainerUploadBlockParam object { file_id, type, cache_control }` + - `ContainerUploadBlockParam object` A content block that represents a file to be uploaded to the container Files uploaded via this block will be available in the container's input directory.
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- `type: "container_upload"` - - `"container_upload"` - - `cache_control: optional CacheControlEphemeral or null` Create a cache control breakpoint at this content block.
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- `type: "json_schema"` - - `"json_schema"` - - `system: optional string or array of TextBlockParam` System prompt.
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- `text: string` + minLength: 1 + - `type: "text"` - `cache_control: optional CacheControlEphemeral or null`
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See [extended thinking](https://platform.claude.com/docs/en/build-with-claude/extended-thinking) for details. - - `ThinkingConfigEnabled object { budget_tokens, type, display }` + - `ThinkingConfigEnabled object` - `budget_tokens: number`
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See [extended thinking](https://platform.claude.com/docs/en/build-with-claude/extended-thinking) for details. + minimum: 1024 + - `type: "enabled"` - - `"enabled"` - - `display: optional "summarized" or "omitted" or null` Controls how thinking content appears in the response. When set to `summarized`, thinking is returned normally. When set to `omitted`, thinking content is redacted but a signature is returned for multi-turn continuity. Defaults to `summarized`.
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- `"omitted"` - - `ThinkingConfigDisabled object { type }` + - `ThinkingConfigDisabled object` - `type: "disabled"` - - `"disabled"` - - - `ThinkingConfigAdaptive object { type, display }` + - `ThinkingConfigAdaptive object` - `type: "adaptive"` - - `"adaptive"` - - `display: optional "summarized" or "omitted" or null` Controls how thinking content appears in the response. When set to `summarized`, thinking is returned normally. When set to `omitted`, thinking content is redacted but a signature is returned for multi-turn continuity. Defaults to `summarized`.
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How the model should use the provided tools. The model can use a specific tool, any available tool, decide by itself, or not use tools at all. - - `ToolChoiceAuto object { type, disable_parallel_tool_use }` + - `ToolChoiceAuto object` The model will automatically decide whether to use tools. - `type: "auto"` - - `"auto"` - - `disable_parallel_tool_use: optional boolean` Whether to disable parallel tool use. Defaults to `false`. If set to `true`, the model will output at most one tool use. - - `ToolChoiceAny object { type, disable_parallel_tool_use }` + - `ToolChoiceAny object` The model will use any available tools. - `type: "any"` - - `"any"` - - `disable_parallel_tool_use: optional boolean` Whether to disable parallel tool use. Defaults to `false`. If set to `true`, the model will output exactly one tool use. - - `ToolChoiceTool object { name, type, disable_parallel_tool_use }` + - `ToolChoiceTool object` The model will use the specified tool with `tool_choice.name`.
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- `type: "tool"` - - `"tool"` - - `disable_parallel_tool_use: optional boolean` Whether to disable parallel tool use. Defaults to `false`. If set to `true`, the model will output exactly one tool use. - - `ToolChoiceNone object { type }` + - `ToolChoiceNone object` The model will not be allowed to use tools. - `type: "none"` - - - `"none"` - `tools: optional array of MessageCountTokensTool`
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See our [guide](https://platform.claude.com/docs/en/agents-and-tools/tool-use/overview) for more details. - - `Tool object { input_schema, name, allowed_callers, 7 more }` - - - `input_schema: object { type, properties, required }` + - `Tool object` + + - `input_schema: object` [JSON schema](https://json-schema.org/draft/2020-12) for this tool's input.
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- `type: "object"` - - `"object"` - - `properties: optional map[unknown] or null` - `required: optional array of string or null`
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This is how the tool will be called by the model and in `tool_use` blocks. + maxLength: 128, minLength: 1, pattern: ^[a-zA-Z0-9_-]{1,128}$ + - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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- `type: optional "custom" or null` - - `"custom"` - - - `ToolBash20250124 object { name, type, allowed_callers, 4 more }` + - `ToolBash20250124 object` - `name: "bash"`
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This is how the tool will be called by the model and in `tool_use` blocks. - - `"bash"` - - `type: "bash_20250124"` - - `"bash_20250124"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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When true, guarantees schema validation on tool names and inputs - - `CodeExecutionTool20250522 object { name, type, allowed_callers, 3 more }` + - `CodeExecutionTool20250522 object` - `name: "code_execution"`
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This is how the tool will be called by the model and in `tool_use` blocks. - - `"code_execution"` - - `type: "code_execution_20250522"` - - `"code_execution_20250522"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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When true, guarantees schema validation on tool names and inputs - - `CodeExecutionTool20250825 object { name, type, allowed_callers, 3 more }` + - `CodeExecutionTool20250825 object` - `name: "code_execution"`
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This is how the tool will be called by the model and in `tool_use` blocks. - - `"code_execution"` - - `type: "code_execution_20250825"` + - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` + + - `"direct"` + - `"code_execution_20250825"` + - `"code_execution_20260120"` + + - `"code_execution_20260521"` + + - `cache_control: optional CacheControlEphemeral or null` + + Create a cache control breakpoint at this content block. + + - `defer_loading: optional boolean` + + If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search. + + - `strict: optional boolean` + + When true, guarantees schema validation on tool names and inputs + + - `CodeExecutionTool20260120 object` + + Code execution tool with REPL state persistence (daemon mode + gVisor checkpoint). + + - `name: "code_execution"` + + Name of the tool. + + This is how the tool will be called by the model and in `tool_use` blocks. + + - `type: "code_execution_20260120"` + - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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When true, guarantees schema validation on tool names and inputs - - `CodeExecutionTool20260120 object { name, type, allowed_callers, 3 more }` - - Code execution tool with REPL state persistence (daemon mode + gVisor checkpoint). + - `CodeExecutionTool20260521 object` + + Code execution tool with REPL state persistence. - `name: "code_execution"`
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This is how the tool will be called by the model and in `tool_use` blocks. - - `"code_execution"` - - - `type: "code_execution_20260120"` + - `type: "code_execution_20260521"` + + - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` + + - `"direct"` + + - `"code_execution_20250825"` - `"code_execution_20260120"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - - - `"direct"` - - - `"code_execution_20250825"` - - - `"code_execution_20260120"` - - `"code_execution_20260521"` - `cache_control: optional CacheControlEphemeral or null`
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When true, guarantees schema validation on tool names and inputs - - `CodeExecutionTool20260521 object { name, type, allowed_callers, 3 more }` - - Code execution tool with REPL state persistence. - - - `name: "code_execution"` - - Name of the tool. - - This is how the tool will be called by the model and in `tool_use` blocks. - - - `"code_execution"` - - - `type: "code_execution_20260521"` - - - `"code_execution_20260521"` - - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - - - `"direct"` - - - `"code_execution_20250825"` - - - `"code_execution_20260120"` - - - `"code_execution_20260521"` - - - `cache_control: optional CacheControlEphemeral or null` - - Create a cache control breakpoint at this content block. - - - `defer_loading: optional boolean` - - If true, tool will not be included in initial system prompt. Only loaded when returned via tool_reference from tool search. - - - `strict: optional boolean` - - When true, guarantees schema validation on tool names and inputs - - - `BrowserToolset20260801 object { type, allowed_callers, cache_control, configs }` + - `BrowserToolset20260801 object` The browser toolset: a single `tools[]` entry (carrying no `name`) that declares the browser tool family. The model is served
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from its schema. - `type: "browser_toolset_20260801"` - - - `"browser_toolset_20260801"` - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"`
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Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema. - - `MemoryTool20250818 object { name, type, allowed_callers, 4 more }` + - `MemoryTool20250818 object` - `name: "memory"`
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This is how the tool will be called by the model and in `tool_use` blocks. - - `"memory"` - - `type: "memory_20250818"` - - `"memory_20250818"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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When true, guarantees schema validation on tool names and inputs - - `ComputerToolset20260801 object { type, allowed_callers, cache_control, configs }` + - `ComputerToolset20260801 object` The computer toolset: a single `tools[]` entry (carrying no `name`) that declares the computer tool family. The model is
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- `type: "computer_toolset_20260801"` - - `"computer_toolset_20260801"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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Whether this member is offered to the model. Default is per member, per the toolset's documentation. A member whose enabled resolves false is withheld from the served schema. - - `ToolTextEditor20250124 object { name, type, allowed_callers, 4 more }` + - `ToolTextEditor20250124 object` - `name: "str_replace_editor"`
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This is how the tool will be called by the model and in `tool_use` blocks. - - `"str_replace_editor"` - - `type: "text_editor_20250124"` - - `"text_editor_20250124"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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When true, guarantees schema validation on tool names and inputs - - `ToolTextEditor20250429 object { name, type, allowed_callers, 4 more }` + - `ToolTextEditor20250429 object` - `name: "str_replace_based_edit_tool"`
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This is how the tool will be called by the model and in `tool_use` blocks. - - `"str_replace_based_edit_tool"` - - `type: "text_editor_20250429"` - - `"text_editor_20250429"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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When true, guarantees schema validation on tool names and inputs - - `ToolTextEditor20250728 object { name, type, allowed_callers, 5 more }` + - `ToolTextEditor20250728 object` - `name: "str_replace_based_edit_tool"`
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This is how the tool will be called by the model and in `tool_use` blocks. - - `"str_replace_based_edit_tool"` - - `type: "text_editor_20250728"` - - `"text_editor_20250728"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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Maximum number of characters to display when viewing a file. If not specified, defaults to displaying the full file. + minimum: 1 + - `strict: optional boolean` When true, guarantees schema validation on tool names and inputs - - `WebSearchTool20250305 object { name, type, allowed_callers, 7 more }` + - `WebSearchTool20250305 object` - `name: "web_search"`
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This is how the tool will be called by the model and in `tool_use` blocks. - - `"web_search"` - - `type: "web_search_20250305"` - - `"web_search_20250305"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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Maximum number of times the tool can be used in the API request. + exclusiveMinimum: 0 + - `strict: optional boolean` When true, guarantees schema validation on tool names and inputs
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- `type: "approximate"` - - `"approximate"` - - `city: optional string or null` The city of the user. + maxLength: 255, minLength: 1 + - `country: optional string or null` The two letter [ISO country code](https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2) of the user. + maxLength: 2, minLength: 2 + - `region: optional string or null` The region of the user. + maxLength: 255, minLength: 1 + - `timezone: optional string or null` The [IANA timezone](https://nodatime.org/TimeZones) of the user. - - `WebFetchTool20250910 object { name, type, allowed_callers, 8 more }` + maxLength: 255, minLength: 1 + + - `WebFetchTool20250910 object` - `name: "web_fetch"`
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This is how the tool will be called by the model and in `tool_use` blocks. - - `"web_fetch"` - - `type: "web_fetch_20250910"` - - `"web_fetch_20250910"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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Maximum number of tokens used by including web page text content in the context. The limit is approximate and does not apply to binary content such as PDFs. + exclusiveMinimum: 0 + - `max_uses: optional number or null` Maximum number of times the tool can be used in the API request. + exclusiveMinimum: 0 + - `strict: optional boolean` When true, guarantees schema validation on tool names and inputs - - `WebSearchTool20260209 object { name, type, allowed_callers, 7 more }` + - `WebSearchTool20260209 object` - `name: "web_search"`
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This is how the tool will be called by the model and in `tool_use` blocks. - - `"web_search"` - - `type: "web_search_20260209"` - - `"web_search_20260209"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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Maximum number of times the tool can be used in the API request. + exclusiveMinimum: 0 + - `strict: optional boolean` When true, guarantees schema validation on tool names and inputs
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Parameters for the user's location. Used to provide more relevant search results. - - `WebFetchTool20260209 object { name, type, allowed_callers, 8 more }` + - `WebFetchTool20260209 object` - `name: "web_fetch"`
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This is how the tool will be called by the model and in `tool_use` blocks. - - `"web_fetch"` - - `type: "web_fetch_20260209"` - - `"web_fetch_20260209"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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Maximum number of tokens used by including web page text content in the context. The limit is approximate and does not apply to binary content such as PDFs. + exclusiveMinimum: 0 + - `max_uses: optional number or null` Maximum number of times the tool can be used in the API request. + exclusiveMinimum: 0 + - `strict: optional boolean` When true, guarantees schema validation on tool names and inputs - - `WebFetchTool20260309 object { name, type, allowed_callers, 9 more }` + - `WebFetchTool20260309 object` Web fetch tool with use_cache parameter for bypassing cached content.
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This is how the tool will be called by the model and in `tool_use` blocks. - - `"web_fetch"` - - `type: "web_fetch_20260309"` - - `"web_fetch_20260309"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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Maximum number of tokens used by including web page text content in the context. The limit is approximate and does not apply to binary content such as PDFs. + exclusiveMinimum: 0 + - `max_uses: optional number or null` Maximum number of times the tool can be used in the API request. + exclusiveMinimum: 0 + - `strict: optional boolean` When true, guarantees schema validation on tool names and inputs
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Whether to use cached content. Set to false to bypass the cache and fetch fresh content. Only set to false when the user explicitly requests fresh content or when fetching rapidly-changing sources. - - `WebSearchTool20260318 object { name, type, allowed_callers, 8 more }` + - `WebSearchTool20260318 object` - `name: "web_search"`
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This is how the tool will be called by the model and in `tool_use` blocks. - - `"web_search"` - - `type: "web_search_20260318"` - - `"web_search_20260318"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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Maximum number of times the tool can be used in the API request. + exclusiveMinimum: 0 + - `response_inclusion: optional "full" or "excluded"` How this tool's result blocks appear in the API response when the result was consumed by a completed code_execution call in the same turn. 'full' returns the complete content (default). 'excluded' drops the nested server_tool_use and result block pair entirely. Results from direct calls, or from code_execution calls that paused before completing, are always returned in full so they can be sent back on the next turn.
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Parameters for the user's location. Used to provide more relevant search results. - - `WebFetchTool20260318 object { name, type, allowed_callers, 10 more }` + - `WebFetchTool20260318 object` - `name: "web_fetch"`
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This is how the tool will be called by the model and in `tool_use` blocks. - - `"web_fetch"` - - `type: "web_fetch_20260318"` - - `"web_fetch_20260318"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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Maximum number of tokens used by including web page text content in the context. The limit is approximate and does not apply to binary content such as PDFs. + exclusiveMinimum: 0 + - `max_uses: optional number or null` Maximum number of times the tool can be used in the API request. + exclusiveMinimum: 0 + - `response_inclusion: optional "full" or "excluded"` How this tool's result blocks appear in the API response when the result was consumed by a completed code_execution call in the same turn. 'full' returns the complete content (default). 'excluded' drops the nested server_tool_use and result block pair entirely. Results from direct calls, or from code_execution calls that paused before completing, are always returned in full so they can be sent back on the next turn.
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Whether to use cached content. Set to false to bypass the cache and fetch fresh content. Only set to false when the user explicitly requests fresh content or when fetching rapidly-changing sources. - - `ToolSearchToolBm25_20251119 object { name, type, allowed_callers, 3 more }` + - `ToolSearchToolBm25_20251119 object` - `name: "tool_search_tool_bm25"`
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This is how the tool will be called by the model and in `tool_use` blocks. + - `type: "tool_search_tool_bm25_20251119" or "tool_search_tool_bm25"` + + - `"tool_search_tool_bm25_20251119"` + - `"tool_search_tool_bm25"` - - `type: "tool_search_tool_bm25_20251119" or "tool_search_tool_bm25"` - - - `"tool_search_tool_bm25_20251119"` - - - `"tool_search_tool_bm25"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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When true, guarantees schema validation on tool names and inputs - - `ToolSearchToolRegex20251119 object { name, type, allowed_callers, 3 more }` + - `ToolSearchToolRegex20251119 object` - `name: "tool_search_tool_regex"`
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This is how the tool will be called by the model and in `tool_use` blocks. + - `type: "tool_search_tool_regex_20251119" or "tool_search_tool_regex"` + + - `"tool_search_tool_regex_20251119"` + - `"tool_search_tool_regex"` - - `type: "tool_search_tool_regex_20251119" or "tool_search_tool_regex"` - - - `"tool_search_tool_regex_20251119"` - - - `"tool_search_tool_regex"` - - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"` - `"direct"`
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When true, guarantees schema validation on tool names and inputs -### Returns - -- `MessageTokensCount object { input_tokens }` +## Returns + +- `MessageTokensCount object` - `input_tokens: number` The total number of tokens across the provided list of messages, system prompt, and tools. -### Example - -```http +## Example + +```bash curl https://api.anthropic.com/v1/messages/count_tokens \ -H 'Content-Type: application/json' \ -H 'anthropic-version: 2023-06-01' \
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}' ``` -#### Response +### Response (200) ```json {