# MCPJam

An open-source testing and evaluation platform for MCP server developers that emulates 16 client configurations and over 170 models, runs evals against test cases, and gates regressions in CI/CD.

MCPJam is a testing and evaluation platform for developers building Model Context Protocol servers, MCP apps and ChatGPT apps. It interactively tests a server's tools, prompts, resources and authorization flows across 16 client configurations and more than 170 models, since clients such as ChatGPT, Claude and Cursor each read a server slightly differently, and shows where a server's behavior diverges between them.

A playground provides a cross-client chat interface with full request and response tracing for every tool call, agent step and JSON-RPC message, including emulation of the OpenAI Apps SDK and MCP app UI widgets. An OAuth debugger visualizes each step of an OAuth or dynamic client registration exchange to find where an authorization flow breaks, across several protocol versions, and evals can be run against test cases and gated in CI/CD to catch regressions before deployment.

It runs as a hosted app with no install, or locally for HTTP, HTTPS and local STDIO servers via a single command.

Website: https://www.mcpjam.com/