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### Client toolsets

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11---

22title: Tool reference

33url: https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-reference

4description: Directory of Anthropic-provided tools and reference for optional tool definition properties.

4description: Directory of Anthropic-provided server tools, client tools, and client toolsets, plus reference for optional tool definition properties.

55---

77This page is a reference for the tools Anthropic provides and the optional properties you can set on any tool definition. For a conceptual introduction to tool use, see [Tool use with Claude](https://platform.claude.com/docs/en/agents-and-tools/tool-use/overview). For guidance on implementing tool use in your application, see [Define tools](https://platform.claude.com/docs/en/agents-and-tools/tool-use/define-tools).

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1010

1111Anthropic 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.

1212

14| -------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------- | --------- | --------------------------------------------------------- |

24| [Computer use tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool) | `computer_toolset_20260801` `computer_20251124` `computer_20250124` | Client | GA Beta: `computer-use-2025-11-24` Beta: `computer-use-2025-01-24` |

2526

2627For model compatibility, see each tool's page. Supported models vary by tool and by tool version.

2728

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3940* **Model-keyed:** `text_editor_20250728` is for Claude 4 and later models and `text_editor_20250124` is for earlier models. The version you use depends on the model you target.

4041* **Variant, not version:** `tool_search_tool_regex_20251119` and `tool_search_tool_bm25_20251119` are two search algorithms released together. Neither supersedes the other.

4142* **Legacy:** `code_execution_20250522` supports only Python. `code_execution_20250825` adds Bash and file operations.

43* **Successor:** `computer_toolset_20260801` is the generally available successor to the beta `computer_20251124` and `computer_20250124` versions, which remain available for existing integrations and for models that don't support the toolset ([Earlier tool versions](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool#earlier-tool-versions)). `browser_toolset_20260801` is the first version of the browser use tool. Both are [client toolsets](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-reference#client-toolsets).

4244

4345The `mcp_toolset` type is not date-versioned; versioning is carried in the `anthropic-beta` header instead.

4446

47### Client toolsets

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.

51Client 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.

53```json

54{

55 "type": "browser_toolset_20260801",

56 "configs": {

57 "javascript_exec": { "enabled": true }

58 },

59 "cache_control": { "type": "ephemeral" }

60}

61```

63`configs` adjusts individual members:

65* Keys are member names, and each value accepts only `enabled` and `defer_loading`.

66* A member you omit keeps its defaults. An absent value, `{}`, and a restated default are equivalent.

67* 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`.

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.

72`cache_control` goes on the entry only; for 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).

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`.

76**Not supported on toolset entries.** The API rejects each of these with an `invalid_request_error`:

78* `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).

80* 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)).

81* 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`.

82* A `tool_choice` of type `tool` that names the toolset or a member (use `auto`, `any`, or `none`).

83* Two entries of the same toolset, or another tool that carries that toolset's name: a tool named `computer` alongside `computer_toolset_20260801`, or a tool named `browser` alongside `browser_toolset_20260801`. The two toolsets can be declared together.

4585## Tool definition properties

4686

4787Every tool in the `tools` array, including user-defined tools, accepts optional properties that control how the tool is loaded, who can call it, and how its inputs are validated. These properties compose: you can set `defer_loading` and `cache_control` and `strict` on the same tool.

4888

50| ----------------------- | --------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------- |

53| `defer_loading` | Exclude the tool from the initial system prompt; load it on demand when tool search returns a `tool_reference` for it | All tools (for `mcp_toolset`, see [tool configuration](https://platform.claude.com/docs/en/agents-and-tools/mcp-connector#mcp-toolset-configuration)) | [Tool search tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-search-tool) |

54| `allowed_callers` | Restrict which callers can call the tool | All tools except `mcp_toolset` | [Programmatic tool calling](https://platform.claude.com/docs/en/agents-and-tools/tool-use/programmatic-tool-calling#the-allowed-callers-field) |

55| `input_examples` | Provide example input objects to help Claude understand how to call the tool | User-defined and Anthropic-schema client tools. Not available on server tools. | [Define tools](https://platform.claude.com/docs/en/agents-and-tools/tool-use/define-tools#providing-tool-use-examples) |

56| `eager_input_streaming` | Enable fine-grained input streaming (`true`) or keep standard buffered streaming (`false`) for this tool | User-defined tools only | [Fine-grained tool streaming](https://platform.claude.com/docs/en/agents-and-tools/tool-use/fine-grained-tool-streaming) |

90| ----------------------- | --------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------- |

91| `cache_control` | Set a prompt-cache breakpoint at this tool definition | All tools (on `computer_toolset_20260801` and `browser_toolset_20260801`, set it on the toolset entry itself, not inside member `configs`) | [Prompt caching](https://platform.claude.com/docs/en/build-with-claude/prompt-caching) |

92| `strict` | Guarantee schema validation on tool names and inputs | All tools except `mcp_toolset`, `computer_toolset_20260801`, and `browser_toolset_20260801` | [Strict tool use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/strict-tool-use) |

93| `defer_loading` | Exclude the tool from the initial system prompt; load it on demand when tool search returns a `tool_reference` for it | All tools (for `mcp_toolset`, see [tool configuration](https://platform.claude.com/docs/en/agents-and-tools/mcp-connector#mcp-toolset-configuration)). On the computer use and browser use toolsets, set it per member inside `configs`; see [Client toolsets](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-reference#client-toolsets). | [Tool search tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-search-tool) |

94| `allowed_callers` | Restrict which callers can call the tool | All tools except `mcp_toolset` (on `computer_toolset_20260801` and `browser_toolset_20260801`, only `["direct"]` is accepted; see [Client toolsets](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-reference#client-toolsets)) | [Programmatic tool calling](https://platform.claude.com/docs/en/agents-and-tools/tool-use/programmatic-tool-calling#the-allowed-callers-field) |

95| `input_examples` | Provide example input objects to help Claude understand how to call the tool | User-defined and Anthropic-schema client tools, except `computer_toolset_20260801` and `browser_toolset_20260801`. Not available on server tools. | [Define tools](https://platform.claude.com/docs/en/agents-and-tools/tool-use/define-tools#providing-tool-use-examples) |

96| `eager_input_streaming` | Enable fine-grained input streaming (`true`) or keep standard buffered streaming (`false`) for this tool | User-defined tools only | [Fine-grained tool streaming](https://platform.claude.com/docs/en/agents-and-tools/tool-use/fine-grained-tool-streaming) |

5797

5898### `allowed_callers` values

5999

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