1,120 pages for message.

effort Claude Developer Platform · in the page build-with-claude/effort …available on all supported models with no beta header required. [Per-message effort](https://platform.claude.com/docs/en/build-with-claude/effort#change-effort-mid-conversation-beta) is in beta. <Ti… extended-thinking Claude Developer Platform · in the page build-with-claude/extended-thinking …model. </Warning> <Note> If a request fails with a 400 error whose message starts with `"thinking.type.enabled" is not supported`, your model uses adaptive thinking instead. See [Troubleshooting th… fallback-credit Claude Developer Platform · in the page build-with-claude/fallback-credit …| The refused request body, unchanged, plus one appended assistant message whose `content` echoes the refused response's `content`. The retry model continues the response from where the refused mod… fast-mode Claude Developer Platform · in the page build-with-claude/fast-mode …ader. <CodeGroup> ```bash cURL curl https://api.anthropic.com/v1/messages \ -H "x-api-key: $ANTHROPIC_API_KEY" \ -H "anthropic-version: 2023-06-01" \ -H "content-type: application/jso… files Claude Developer Platform · in the page build-with-claude/files …de/files description: Upload files once, reference them by file_id in Messages requests, and download outputs created by skills or the code execution tool. featureMetadata: status: ga zdr: not-eli… handling-stop-reasons Claude Developer Platform · in the page build-with-claude/handling-stop-reasons …tool use, paused turns, and refusals in your application. --- Every Messages API response includes a `stop_reason` field that tells you why Claude stopped generating. Check this field to decide whet… mid-conversation-effort-example Claude Developer Platform · in the page build-with-claude/mid-conversation-effort-example …multiagent fan-out, switched on and off with mid-conversation system messages. --- An orchestration mode is a session-level switch: when it is on, the model puts maximum thoroughness behind every su… multilingual-support Claude Developer Platform · in the page build-with-claude/multilingual-support …tion. <CodeGroup> ```bash cURL curl https://api.anthropic.com/v1/messages \ -H "content-type: application/json" \ -H "x-api-key: $ANTHROPIC_API_KEY" \ -H "anthropic-version: 2023-06-0… overview Claude Developer Platform · in the page build-with-claude/overview …as though the conversation had been on the new model from the start. Message Batches results do not include fallback credit tokens. | Not ZDR eligible\*… pdf-support Claude Developer Platform · in the page build-with-claude/pdf-support …## Send your first PDF request Start with a simple example using the Messages API. You can provide PDFs to Claude in three ways: 1. As a URL reference to a PDF hosted online 2. As a base64-encoded P… preserved-thinking Claude Developer Platform · in the page build-with-claude/preserved-thinking …ing block has changed.** The top-level `system` prompt, `tools`, and `messages` before the block are its prefix. If the prefix differs from what you sent when the block was produced, that block and ev… Request 2 caches its request content (not the response) Claude Developer Platform · in the page build-with-claude/prompt-caching …nversations grow. Best for multi-turn conversations where the growing message history should be cached automatically. * **[Explicit cache breakpoints](https://platform.claude.com/docs/en/build-with-cl… claude-prompting-best-practices Claude Developer Platform · in the page build-with-claude/prompt-engineering/claude-prompting-best-practices …tasks, user-facing progress updates, tool use in chat, mid-turn user messages, verification on coding tasks, tool-call handling, complex visual inputs, and safeguard refusals. | | Claude Sonnet 5… prompting-claude-fable-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-fable-5 …s already made, or narrate options you will not pursue in user-facing messages. If you are weighing a choice, give a recommendation, not an exhaustive survey. This does not apply to thinking blocks. `… Delivering work Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-fable-5-1 …hains. Users see the agent go quiet for minutes at a time, or a final message that covers only the last step rather than the whole task. First, check that your client receives progress updates at all… prompting-claude-haiku-5-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-haiku-5-5 …th your own tools, early stopping, coding verification, mid-turn user messages, system prompt adherence in chatbots, reasoning in user-facing text, and refusals." --- This guide covers the prompting… prompting-claude-opus-4-8 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-opus-4-8 …laude Opus 4.7 (1M context window default and mid-conversation system messages), see [Migrating to Claude Opus 5.5 from Claude Opus 4.7](https://platform.claude.com/docs/en/models/opus-5-5/migration-g… prompting-claude-opus-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-opus-5 …gentic work: it tends to announce what it is about to do, and its per-message output in agentic sessions is often longer than prior models'. It benefits from explicit guidance on how to communicate wi… prompting-claude-opus-5-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-opus-5-5 …n, complex visual inputs, multiapp workflows, and pasted text in user messages." --- This guide covers the prompting patterns specific to Claude Opus 5.5. For the model's capabilities and API changes… prompting-claude-sonnet-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-sonnet-5 …g agentic traces. If you've added scaffolding to force interim status messages ("After every 3 tool calls, summarize progress"), try removing it. If you find that the length or contents of Claude Sonn… prompting-claude-sonnet-5-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-sonnet-5-5 …up-front thinking, JSON output, progress updates, tool use, mid-turn messages, coding verification, tool calls, visual inputs, and refusals." --- This guide covers the prompting patterns specific to… refusals-and-fallback Claude Developer Platform · in the page build-with-claude/refusals-and-fallback …```bash cURL curl --fail-with-body -sS https://api.anthropic.com/v1/messages \ -H "x-api-key: $ANTHROPIC_API_KEY" \ -H "anthropic-version: 2023-06-01" \ -H "anthropic-beta: server-side-f… search-results Claude Developer Platform · in the page build-with-claude/search-results …. No beta header is required: search results are part of the standard Messages API. ## How it works Search results can be provided in two ways: 1. **From tool calls:** Your custom tools return sear… skills-guide Claude Developer Platform · in the page build-with-claude/skills-guide …the-real-world-with-agent-skills). </Note> Skills integrate with the Messages API through the [code execution tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/code-execution-tool).… streaming Claude Developer Platform · in the page build-with-claude/streaming --- title: Streaming messages url: https://platform.claude.com/docs/en/build-with-claude/streaming description: Stream Messages API responses incrementally with server-sent events, including text, too… structured-outputs Claude Developer Platform · in the page build-with-claude/structured-outputs …<Tab title="cURL"> ```bash curl https://api.anthropic.com/v1/messages \ -H "content-type: application/json" \ -H "x-api-key: $ANTHROPIC_API_KEY" \ -H "anthropic-version: 202… task-budgets Claude Developer Platform · in the page build-with-claude/task-budgets …ader: <CodeGroup> ```bash cURL curl https://api.anthropic.com/v1/messages \ -N \ -H "x-api-key: $ANTHROPIC_API_KEY" \ -H "anthropic-version: 2023-06-01" \ -H "anthropic-beta: task… thinking Claude Developer Platform · in the page build-with-claude/thinking …nking#thinking-with-tool-use). For the full response format, see the [Messages API reference](https://platform.claude.com/docs/en/api/messages/create). ## Configuring thinking On most models, thinki… thinking-steering-and-cost Claude Developer Platform · in the page build-with-claude/thinking-steering-and-cost …ply Claude thinks with effort levels, system prompt guidance, and per-message steering, and understand thinking's cost and pricing. --- <Note> To learn how zero data retention (ZDR) applies to this… thinking-tool-workflows Claude Developer Platform · in the page build-with-claude/thinking-tool-workflows …when you return a tool result, the thinking blocks from the assistant message must come back with it. * [Echo the assistant message exactly as received](https://platform.claude.com/docs/en/build-with-… thinking-troubleshooting Claude Developer Platform · in the page build-with-claude/thinking-troubleshooting …r it each start from a symptom you observe, so you can match an error message or unexpected response directly to its cause and fix. To learn how thinking works, see the [Thinking](https://platform.cla… token-counting Claude Developer Platform · in the page build-with-claude/token-counting …n/build-with-claude/token-counting description: Count the tokens in a message before you send it to Claude. Use token counts to manage rate limits and costs, make model routing decisions, and fit prom… vision Claude Developer Platform · in the page build-with-claude/vision …layground) in the Claude Console. Add images directly to any **User** message block. * API request. See the following examples. On the API, provide images to Claude as `image` content blocks using on… vision-coordinates Claude Developer Platform · in the page build-with-claude/vision-coordinates …essing it, so a successful count doesn't mean the image is within the Messages API's [request limits](https://platform.claude.com/docs/en/build-with-claude/vision#request-limits). An image can count s… API usage primer for Claude Claude Developer Platform · in the page claude_api_primer …Claude API. It gives explanation and examples of model IDs/the basic messages API, tool use, streaming, thinking, and nothing else. --- # API usage primer for Claude > This guide is designed to giv… apply Claude Developer Platform · in the page cli-sdks-libraries/cli/apply …ents/`: the frontmatter is the request body and the prose becomes the message that starts each session. * A [skill](https://platform.claude.com/docs/en/managed-agents/skills) is a directory with a `SK… On a remote host without a browser: Claude Developer Platform · in the page cli-sdks-libraries/cli/authentication …#global-flags). The value must be a `wrkspc_...` ID. ```bash CLI ant messages create \ --workspace-id wrkspc_01... \ --model claude-opus-5-5 \ --max-tokens 1024 \ --message '{role: user, cont… quickstart Claude Developer Platform · in the page cli-sdks-libraries/cli/quickstart …, see the [API reference](https://platform.claude.com/docs/en/api/cli/messages/create). This page gets you to a working command. For everything else the CLI does, see [Using the CLI](https://platform.… scripting Claude Developer Platform · in the page cli-sdks-libraries/cli/scripting …" /* ... */ } ``` </Step> <Step title="Send a user message"> Copy the session `id` from the previous output into `--session-id`: ```bash ant beta:sessions:events send \… sessions-connect Claude Developer Platform · in the page cli-sdks-libraries/cli/sessions-connect …o a Claude Managed Agents session to follow its transcript live, send messages, allow or deny tool calls, or open the session viewer in your browser. --- `ant beta:sessions connect` attaches your ter… using Claude Developer Platform · in the page cli-sdks-libraries/cli/using …to opt into a different schema version). ```bash ant models list ant messages create --model claude-opus-5-5 --max-tokens 1024 ... ant beta:agents retrieve --agent-id agent_01... ant beta:sessions:ev… apple-foundation-models Claude Developer Platform · in the page cli-sdks-libraries/libraries/apple-foundation-models …> <Info> Claude for Foundation Models is **not** a general-purpose Messages API client. Its public surface is the Foundation Models provider conformance plus the configuration types that reach it (… openai-sdk Claude Developer Platform · in the page cli-sdks-libraries/libraries/openai-sdk …ons.create( model="claude-opus-5-5", # Claude model name messages=[ {"role": "system", "content": "You are a helpful assistant."}, {"role": "user", "content": "Who are… overview Claude Developer Platform · in the page cli-sdks-libraries/overview …ell scripting and interactive use. * **Client SDKs:** General-purpose Messages API clients for Python, TypeScript, C#, Go, Java, PHP, and Ruby. Each SDK provides idiomatic interfaces, type safety, and… csharp Claude Developer Platform · in the page cli-sdks-libraries/sdks/csharp …sage ```csharp using System; using Anthropic; using Anthropic.Models.Messages; AnthropicClient client = new(); MessageCreateParams parameters = new() { MaxTokens = 1024, Messages = [new Use… go Claude Developer Platform · in the page cli-sdks-libraries/sdks/go …ropic-api-key"), // defaults to os.LookupEnv("ANTHROPIC_API_KEY") ) message, err := client.Messages.New(context.TODO(), anthropic.MessageNewParams{ MaxTokens: 1024, Messages: []anthropic.Message… java Claude Developer Platform · in the page cli-sdks-libraries/sdks/java …opic.client.okhttp.AnthropicOkHttpClient; import com.anthropic.models.messages.Message; import com.anthropic.models.messages.MessageCreateParams; import com.anthropic.models.messages.Model; // Config… php Claude Developer Platform · in the page cli-sdks-libraries/sdks/php …default value must be set by name. ```php $client = new Client(); $message = $client->messages->create( maxTokens: 1024, messages: [['role' => 'user', 'content' => 'Hello, Claude']], mo… For Amazon Bedrock support Claude Developer Platform · in the page cli-sdks-libraries/sdks/python …nd can be omitted api_key=os.environ.get("ANTHROPIC_API_KEY"), ) message = client.messages.create( max_tokens=1024, messages=[ { "role": "user", "content":… Automatically handles tool execution loop Claude Developer Platform · in the page cli-sdks-libraries/sdks/ruby …ENV["ANTHROPIC_API_KEY"] # This is the default and can be omitted ) message = anthropic.messages.create( max_tokens: 1024, messages: [{role: "user", content: "Hello, Claude"}], model: Anthropi…