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HomeDocsClaude Code CLI 4 Oct 2026
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Connect to external tools with MCP changedagent-sdk/mcp

Nearest release: v2.1.289, published 9 hours before upstream edited the page. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.

Upstream edited this page at 4 Oct 2026 06:10 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 4 Oct 2026 06:37 UTC.

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### A tool is missing from an SDK MCP server

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866866</CodeGroup>
867867 
868### A tool is missing from an SDK MCP server
869 
870In the TypeScript SDK, when a tool's input schema can't be converted to JSON Schema, the server you created with [`createSdkMcpServer()`](/docs/en/agent-sdk/typescript#createsdkmcpserver) leaves that tool out when it lists its tools. The SDK emits a warning at that point. Under Node.js the warning is a process warning with code `CLAUDE_SDK_MCP_TOOL_SCHEMA_UNCONVERTIBLE`, and it starts with this text:
871 
872```text theme={null}
873Tool "<name>" on SDK MCP server "<server>" was left out of the server's tool list, because its input schema cannot be converted to JSON Schema
874```
875 
876The rest of the warning gives the conversion error's message when it has one, then says what to check and change.
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878Before TypeScript Agent SDK v0.3.286, one unconvertible schema made the server's whole tool listing fail without this warning, so none of that server's tools reached Claude.
879 
868880### Connection timeouts
869881 
870882MCP server connections time out after 30 seconds by default. To change how long a running tool call may take, set [`MCP_TOOL_TIMEOUT`](/docs/en/env-vars). If your server takes longer to start, the connection fails. Raise the connection limit with the [`MCP_TIMEOUT`](/docs/en/env-vars) environment variable, in milliseconds. For servers that need more startup time, also consider:
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