Responds to ping requests

MCP clients send ping requests to verify a server is alive before timing out a connection or showing an error to the user. A server that returns -32601 Method not found on ping tells the client it is disconnected, triggering reconnection logic or user-visible errors even when the server is running fine. A server that returns a non-standard value (e.g., the string "pong" instead of an empty object {}) breaks clients that validate response shape. Ping is cheap to implement correctly and expensive to get wrong.

The MCP SDK handles ping automatically — do not override it. For custom implementations, add a case for ping that returns an empty result object.

// src/transport/handler.ts — ping handler
if (message.method === 'ping') {
  return {
    jsonrpc: '2.0',
    id: message.id,
    result: {}  // empty object, not null, not 'pong'
  }
}

Verify the ping handler is working by sending { "jsonrpc": "2.0", "method": "ping", "id": 1 } directly to your server and confirming the response is { "jsonrpc": "2.0", "id": 1, "result": {} }.

• ID: mcp-server.transport-protocol.ping-support

• Severity: low

• What to look for: Enumerate whether the server handles ping requests and responds with a valid JSON-RPC response. Count ping handler implementations. The MCP spec defines a ping method that clients use to check if the server is alive. Check that the server handles ping requests and returns an empty result {}. For SDK-based servers, this is built in — verify it's not accidentally disabled or overridden. For custom implementations, check for a ping case in the message handler.

• Pass criteria: The server responds to ping requests with an empty result object {}. SDK-based servers get this automatically. At least 1 ping handler must respond within 100ms.

• Fail criteria: Custom server does not handle ping (returns method-not-found), or SDK server has ping handling accidentally overridden.

• Skip (N/A) when: All checks skip when no MCP server is detected.

• Cross-reference: For timeout handling, see timeout-handling.

• Detail on fail: "Custom message handler has no case for 'ping' method — returns -32601 method not found. Clients will consider the server unresponsive" or "Ping handler returns 'pong' string instead of empty object {} — non-standard response"

• Remediation: Ping is simple but important for client health checks:

  // Ping is handled automatically by the MCP SDK in src/index.ts
  // Verify with: { "jsonrpc": "2.0", "method": "ping", "id": 1 }
  

  // Custom implementation
  if (message.method === 'ping') {
    return { jsonrpc: '2.0', id: message.id, result: {} }
  }
  
  // SDK-based servers handle this automatically — just don't override it