Extend with tools
Give Claude custom tools
Define custom tools with the Claude Agent SDK’s in-process MCP server so Claude can call your functions, hit your APIs, and perform domain-specific operations.
Custom tools extend the Agent SDK by letting you define your own functions that Claude can call during a conversation. Using the SDK’s in-process MCP server, you can give Claude access to databases, external APIs, domain-specific logic, or any other capability your application needs.