MCP Academy · Lesson

Anatomy of a JSON-RPC Call

id, method, and params in a real MCP message.

Open the Envelope

Let us dissect one real MCP message field by field. A JSON-RPC call is a small JSON object, and four keys carry all of its meaning.

Every message starts with jsonrpc set to the string 2.0. It marks the dialect so both sides parse the rest the same way.

{"jsonrpc": "2.0"}