Scaling AI Agent Infrastructure with the MCP Stateless updates- Google Developers Blog

What this post added

This post details the evolution of the Model Context Protocol (MCP) from a stateful to a stateless protocol. Key changes include the removal of the `initialize/initialized` handshake and the `Mcp-Session-Id` header, making every request self-describing and independent. Protocol version, client info, and capabilities are now included in a `_meta` field within each request. HTTP Standardization (SEP-2243) introduces headers like `Mcp-Protocol-Version`, `Mcp-Method`, and `Mcp-Name` for routing and auditing without deep packet inspection. Intelligent Caching with `ttlMs` (SEP-2549) is introduced for caching tool and resource results. Multi Round-Trip Requests (MRTR) (SEP-2322) enable stateless handling of server-to-client requests by returning `InputRequiredResult` with a `requestState` payload. The Tasks Extension (SEP-2663) allows for asynchronous, non-blocking execution of long-running tools by returning a `taskId` immediately. Security enhancements include Issuer Verification (RFC 9207) and Resource Indicators (RFC 8707).