MCP Integration

In-process MCP servers

SdkControlTransport in source (not documented here; referenced by name) provides the transport mechanism for SDK-spawned MCP servers. Allows tool definitions to live in application code without separate server process.

External MCP servers

Connect to stdio, HTTP, or SSE servers via mcpServers config. Server name becomes tool prefix: mcp__<server>__<tool>.

mcpServers: {
  github: {
    command: "npx",
    args: ["-y", "@modelcontextprotocol/server-github"],
    env: { GITHUB_TOKEN: process.env.GITHUB_TOKEN }
  }
},
allowedTools: ["mcp__github__list_issues"]

Tool prefixing

By default, MCP tools are prefixed mcp__. Set CLAUDE_AGENT_SDK_MCP_NO_PREFIX=1 to disable prefixing (use with caution; can collide with built-in tool names).

MCP configuration

Per-session in options.mcpServers or global in .mcp.json (loaded when settingSources includes 'project').

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