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1---2title: Tool reference3url: https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-reference4description: Directory of Anthropic-provided server tools, client tools, and client toolsets, plus reference for optional tool definition properties.5---67This 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).89## Anthropic-provided tools1011Anthropic 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.1213| Tool | `type` | Execution | [Beta header](https://platform.claude.com/docs/en/api/beta-headers) |14| -------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------- | --------- | ------------------------------------------------------------------- |15| [Web search tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/web-search-tool) | `web_search_20260318` `web_search_20260209` `web_search_20250305` | Server | None |16| [Web fetch tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/web-fetch-tool) | `web_fetch_20260318` `web_fetch_20260309` `web_fetch_20260209` `web_fetch_20250910` | Server | None |17| [Code execution tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/code-execution-tool) | `code_execution_20260521` `code_execution_20260120` `code_execution_20250825` | Server | None |18| [Advisor tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/advisor-tool) | `advisor_20260301` | Server | `advisor-tool-2026-03-01` |19| [Tool search tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-search-tool) | `tool_search_tool_regex_20251119` `tool_search_tool_bm25_20251119` | Server | None |20| [MCP connector](https://platform.claude.com/docs/en/agents-and-tools/mcp-connector) | `mcp_toolset` | Server | `mcp-client-2025-11-20` |21| [Memory tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/memory-tool) | `memory_20250818` | Client | None |22| [Bash tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/bash-tool) | `bash_20250124` | Client | None |23| [Text editor tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/text-editor-tool) | `text_editor_20250728` `text_editor_20250124` | Client | None |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 | None `computer-use-2025-11-24` `computer-use-2025-01-24` |25| [Browser use tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/browser-use-tool) | `browser_toolset_20260801` | Client | None |2627For model compatibility, see each tool's page. Supported models vary by tool and by tool version.2829<Note>30 The tool search `type` values also accept undated aliases: `tool_search_tool_regex` and `tool_search_tool_bm25`. These resolve to the latest dated version.31</Note>3233### Tool versioning3435Most Anthropic-provided tools carry a `_YYYYMMDD` suffix in the `type` string. A new version is released when the tool's behavior, schema, or model support changes. Older versions remain available so that existing integrations continue to work.3637When a tool has multiple active versions, the relationship between them varies:3839* **Capability-keyed:** `web_search_20260209` and `web_fetch_20260209` add dynamic content filtering over their predecessors; `web_fetch_20260309` adds a cache-bypass option; `web_search_20260318` and `web_fetch_20260318` add response-inclusion control. `code_execution_20260120` adds [programmatic tool calling](https://platform.claude.com/docs/en/agents-and-tools/tool-use/programmatic-tool-calling) from within the sandbox; `code_execution_20260521` discloses the per-cell time limit in the tool description. In each case, both the new and old versions are current; which one you use depends on whether you need the new capability.40* **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.41* **Variant, not version:** `tool_search_tool_regex_20251119` and `tool_search_tool_bm25_20251119` are two search algorithms released together. Neither supersedes the other.42* **Legacy:** `code_execution_20250522` supports only Python. `code_execution_20250825` adds Bash and file operations.43* **Successor:** `computer_toolset_20260801` is the stable 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).4445The `mcp_toolset` type is not date-versioned; versioning is carried in the `anthropic-beta` header instead.4647### Client toolsets4849The [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.5051Client 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.5253```json54{55 "type": "browser_toolset_20260801",56 "configs": {57 "javascript_exec": { "enabled": true }58 },59 "cache_control": { "type": "ephemeral" }60}61```6263`configs` adjusts individual members:6465* 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`.6970Set `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.7172`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).7374**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`.7576**Not supported on toolset entries.** The API rejects each of these with an `invalid_request_error`:7778* `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.8485## Tool definition properties8687Every 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.8889| Property | Purpose | Available on | Detailed guide |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) |9798### `allowed_callers` values99100`allowed_callers` is an array that accepts any combination of:101102| Value | Meaning |103| --------------------------- | ----------------------------------------------------------------------------------------------------------------- |104| `"direct"` | The model can call this tool directly in a `tool_use` block. This is the default if `allowed_callers` is omitted. |105| `"code_execution_20260120"` | Code running inside a `code_execution_20260120` or later sandbox can call this tool. |106107Both `"code_execution_20260120"` and `"code_execution_20260521"` are accepted in `allowed_callers` and are interchangeable: a request using either code-execution tool version satisfies tools that list either caller. Response blocks always tag the caller as `code_execution_20260120` regardless of which version the request declared.108109Omitting `"direct"` from the array (for example, `"allowed_callers": ["code_execution_20260120"]`) guides Claude to call the tool only from within code execution. The response's `tool_use` block includes a `caller` field that identifies which caller called the tool. See [Programmatic tool calling](https://platform.claude.com/docs/en/agents-and-tools/tool-use/programmatic-tool-calling#the-allowed-callers-field) for the full treatment, including the `caller` response shape and error behavior.110111### `defer_loading` and prompt caching112113Tools with `defer_loading: true` are stripped from the rendered tools section before the cache key is computed. They don't appear in the system-prompt prefix at all. When tool search discovers a deferred tool and returns a `tool_reference` for it, the tool's full definition is expanded inline at that point in the conversation body, not in the prefix.114115This means `defer_loading: true` preserves your prompt cache. You can add deferred tools to a request without invalidating an existing cache entry, and the cache remains valid across the turn where the tool is discovered and the turn where it's called.116117To learn how to combine `defer_loading` with `cache_control` breakpoints, see the [Tool search tool prompt caching guidance](https://platform.claude.com/docs/en/agents-and-tools/tool-use/tool-search-tool#prompt-caching).118