Mechanism◆Article
MCP lets a host application route a user request through an embedded MCP client to the correct MCP server, which executes the tool call and returns a structured response the agent uses to continue reasoning.
MCP standardizes how an agent's host application discovers and calls tools through an MCP client-server exchange. ✦ AI generated
ByteByteGo · ByteByteGo Newsletter · 2026-07-18 · original ↗
The host app receives the user request, its embedded MCP client formats and routes it to the right MCP server, the server executes the tool call and returns a structured response. The agent uses the result to continue reasoning.
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- ·Host app receives the user request
- ·Embedded MCP client formats and routes it
- ·Correct MCP server executes the tool call
- ·Server returns a structured response
- ·Agent uses result to continue reasoning
- ·Standardizes tool discovery and calling
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Context · 3
Legacy stateful MCP required two HTTP requests — an initialize handshake to obtain a Mcp-Session-Id followed by the actual tool call — while stateless MCP collapses this to a single request, which is much cleaner to implement from both client and server sides and a better fit for scalable web applications that need no server-side session state.Simon Willison · Simon Willison's Weblog · conf 60%I couldn't find a great CLI tool for interactively probing an MCP server, so I had Codex help build mcp-explorer — a stateless Python CLI that needs no installation and runs via uvx against any MCP endpoint.Simon Willison · Simon Willison's Weblog · conf 60%datasette-mcp adds a /-/mcp endpoint to any Datasette instance exposing three tools — list_databases(), get_database_schema(), and read-only execute_sql() — giving agents the ability to run SQL queries against a hosted Datasette instance, and it is a fourth attempt that finally felt releasable thanks to the stateless spec.Simon Willison · Simon Willison's Weblog · conf 60%