Give Claude custom tools changedagent-sdk/custom-tools
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Upstream edited this page at 17 Oct 2026 01:27 UTC, give or take a minute or two: the time comes from Anthropic’s own sitemap rather than from a commit. This site recorded the change at 17 Oct 2026 01:37 UTC.
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152152### Call a custom tool
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154Pass the MCP server you created to `query` via the `mcpServers` option. The key in `mcpServers` becomes the `{server_name}` segment in each tool's fully qualified name: `mcp__{server_name}__{tool_name}`. List that name in `allowedTools` so the tool runs without a permission prompt.
154Pass the MCP server you created to `query` via the `mcpServers` option. Each tool's [fully qualified name](/docs/en/agent-sdk/mcp#tool-naming-convention) is `mcp__{server_name}__{tool_name}`, where `{server_name}` is the key you give the server in `mcpServers`. If the key contains characters such as `.` or spaces, replace them with `_` when you write `{server_name}`. List the fully qualified name in `allowedTools` so the tool runs without a permission prompt.
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156156These snippets reuse the `weatherServer` from the [weather tool example](#weather-tool-example) to ask Claude what the weather is in a specific location.
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