JSON-RPC (in MCP)

Definition

MCP is built on JSON-RPC 2.0, a lightweight remote-procedure-call protocol that encodes requests and responses as JSON messages.

You don't normally see it, but it's why MCP error codes look the way they do — codes like -32000 (connection closed) and -32601 (method not found) are JSON-RPC conventions. Knowing that helps debugging: a -32601 is a protocol/version mismatch, not your config.

Authoritative source: JSON-RPC 2.0 spec