tool-reference changedagents-and-tools/tool-use/tool-reference
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99## Anthropic-provided tools
1010
11Anthropic provides two kinds of tools: **server tools** that execute on Anthropic's infrastructure, and **client tools** where Anthropic defines the schema but your application handles execution. Both kinds appear in your request's `tools` array alongside any user-defined tools.
11Anthropic provides two kinds of tools: **server tools** that run on Anthropic's infrastructure, and **client tools** where Anthropic defines the schema but your application handles execution. Both kinds appear in your request's `tools` array alongside any user-defined tools.
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1313| Tool | `type` | Execution | [Beta header](https://platform.claude.com/docs/en/api/beta-headers) |
1414| -------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------- | --------- | ------------------------------------------------------------------- |
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4646
4747### Client toolsets
4848
49The [computer use tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool) and [browser use tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/browser-use-tool) are Anthropic-defined client toolsets: one entry in `tools` declares a fixed set of member tools whose names, descriptions, and input schemas Anthropic defines, and your application executes every call. The entry takes no `name`, because the dated `type` fixes the member names. `configs`, `cache_control`, and `allowed_callers` (which accepts only `["direct"]`) are optional.
49The [computer use tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool) and [browser use tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/browser-use-tool) are Anthropic-defined client toolsets: one entry in `tools` declares a fixed set of member tools whose names, descriptions, and input schemas Anthropic defines, and your application runs every call. The entry takes no `name`, because the dated `type` fixes the member names. `configs`, `cache_control`, and `allowed_callers` (which accepts only `["direct"]`) are optional.
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5151Client toolsets are Messages API tools. They aren't currently available as agent tools in [Claude Managed Agents](https://platform.claude.com/docs/en/managed-agents/tools), which provides its own built-in agent toolset, MCP toolsets, and custom tools.
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6565* Keys are member names, and each value accepts only `enabled` and `defer_loading`.
6666* A member you omit keeps its defaults. An absent value, `{}`, and a restated default are equivalent.
6767* An unknown member name or any other field in a member's value is rejected, as is a `configs` that disables every member (omit the entry instead).
68* A disabled member is removed from the tools Claude sees. If Claude still names it, return an error `tool_result`.
68* A disabled member is removed from the tools Claude receives. If Claude still names it, return an error `tool_result`.
6969
70Set `defer_loading` per member, never on the entry, and give every enabled member the same value: under [tool search](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-search-tool#deferred-tool-loading) the toolset loads and expands as one definition. When every enabled member defers, only a [tool search tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-search-tool) that isn't itself deferred can surface the toolset, so declare one in the same request. Don't put `cache_control` on a toolset entry whose members defer; set the breakpoint on a non-deferred tool instead, because deferred definitions are not part of the cached prefix.
70Set `defer_loading` for each member, never on the entry, and give every enabled member the same value: under [tool search](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-search-tool#deferred-tool-loading) the toolset loads and expands as one definition. When every enabled member defers, only a [tool search tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-search-tool) that isn't itself deferred can surface the toolset, so declare one in the same request. Don't put `cache_control` on a toolset entry whose members defer; set the breakpoint on a non-deferred tool instead, because deferred definitions are not part of the cached prefix.
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7272`cache_control` goes on the entry only; to learn where the breakpoint lands, including markers inside a batch action, see [Tool use with prompt caching](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-use-with-prompt-caching#cache-control-on-tool-definitions).
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74**Handle member tool calls.** Claude calls a member with a `tool_use` block whose `name` is the member name and whose `toolset_name` is `computer` or `browser`; `input` holds that member's parameters and no `action` field. Dispatch on the `toolset_name` and `name` pair, because a custom tool may share a member's name and the two toolsets share names such as `screenshot`. Only member results echo `toolset_name`. Several member calls in one turn form a batch action that you run in order ([computer use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool#batch-actions), [browser use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/browser-use-tool#batch-actions)). New members arrive only with a new dated `type`.
74**Handle member tool calls.** Claude calls a member with a `tool_use` block whose `name` is the member name and whose `toolset_name` is `computer` or `browser`; `input` holds that member's parameters and no `action` field. Dispatch on the `toolset_name` and `name` pair, because a custom tool might share a member's name and the two toolsets share names such as `screenshot`. Only member results echo `toolset_name`. Several member calls in one turn form a batch action that you run in order ([computer use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool#batch-actions), [browser use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/browser-use-tool#batch-actions)). New members arrive only with a new dated `type`.
7575
7676**Not supported on toolset entries.** The API rejects each of these with an `invalid_request_error`:
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7878* `strict: true` or `input_examples`.
79* `defer_loading` on the entry, or enabled members whose `defer_loading` values differ (set it per member in `configs`, all to the same value).
79* `defer_loading` on the entry, or enabled members whose `defer_loading` values differ (set it for each member in `configs`, all to the same value).
8080* A code execution caller in `allowed_callers` (no [programmatic tool calling](https://platform.claude.com/docs/en/agents-and-tools/tool-use/programmatic-tool-calling)).
8181* The legacy `fine-grained-tool-streaming-2025-05-14` beta header. When you stream, each member's `input` arrives as one complete `input_json_delta`.
8282* A `tool_choice` of type `tool` that names the toolset or a member (use `auto`, `any`, or `none`).
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