Implements initialize method and returns capabilities

The MCP handshake (initialize → server capabilities → notifications/initialized) is a mandatory protocol sequence. A server that does not handle the initialize method returns a method-not-found error on the very first client message, causing immediate disconnection before any tool can be called. Processing tool requests before the handshake completes violates the protocol ordering guarantee and causes undefined behavior in clients that enforce the sequence. This is a baseline conformance requirement with no workaround on the client side.

If using the MCP SDK, the handshake is handled automatically when you call server.connect(transport). Verify your server config includes all capabilities you implement.

// src/index.ts — SDK handles initialize automatically
const server = new Server(
  { name: 'my-server', version: '1.0.0' },
  { capabilities: { tools: { listChanged: true }, resources: {} } }
)
const transport = new StdioServerTransport()
await server.connect(transport)  // handshake negotiated here

For custom implementations, add a handler for initialize that returns protocolVersion, capabilities, and serverInfo, and gates all other method handlers behind an isInitialized flag.