What Is JSON-RPC?
JSON-RPC is a lightweight remote-procedure-call protocol that encodes a method name, parameters, and an id as JSON over any transport. Its simplicity and transport-independence are why newer agent protocols build on it: the Model Context Protocol uses JSON-RPC 2.0 to carry messages between a client and a tool server. It defines requests, responses, errors, and batching, and nothing else — the surrounding protocol supplies the meaning.
A message format, not a framework
JSON-RPC deliberately does very little: it standardises how a call and its result are shaped, including errors and batched calls, and leaves transport and semantics to whatever uses it. That minimalism is why it keeps being chosen for new protocols rather than a heavier framework.
When an agent calls a tool over the Model Context Protocol, the envelope carrying that call is JSON-RPC; the meaning of the method is MCP’s.
Related standards
Questions
How is JSON-RPC different from REST?
REST models resources and uses HTTP verbs; JSON-RPC models method calls and is transport-agnostic, which suits long-lived agent-to-tool sessions.
Is JSON-RPC new?
No — version 2.0 is long-established. Its recent prominence comes from agent protocols adopting it as their message layer.
Keep reading
By Michael Gord · published 2026-10-09 · part of the Agentic Encyclopedia. Dates are the day of publication; events are cited at their own dates.