MCPJam is the open-source testing & evaluations platform for MCP server developers who ship. Interactively test tools, prompts, resources, and authorization across 16 client configurations and 170+ models. Run evals on test cases, get insights on what's breaking, and gate regressions to secure every deployment.
Open the hosted app. No install needed.
... or run MCPJam locally for HTTP/S and local STDIO servers:
npx @mcpjam/inspector@latestClients like ChatGPT, Claude, and Cursor all read your server differently. MCPJam catches those differences, shows where your server breaks, and tells you how to fix it:
- Inspect & debug: Explore your server's tools, resources, and prompts in one place. Test prompts from real LLMs, with full visibility & traces on every JSON-RPC message and OAuth exchange.
- Cross-client evals: Score agent behavior across 16 client configurations — ChatGPT, Claude, Cursor, Copilot, and more — to understand how your MCP integrations perform across all users. Track accuracy, latency, and tool-call performance over time.
- Security & reliability: Automate conformance & behavior checks in CI/CD to catch regressions before they reach production.
Trace view: every tool call, agent step, and JSON-RPC message in one timeline.
| Capability | What it does |
|---|---|
| Playground | Cross-client chat interface that emulates UIs, tool calls, and skills (with full traces). OpenAI Apps SDK and MCP app UIs, text tools, and a Chrome DevTools-style widget emulator. Read more |
| OAuth Debugger | Visualize your OAuth & EMA requests step-by-step to find the source of errors. Guided MCP OAuth conformance checks across protocol versions 03-26, 06-18, 11-25, and 2026-07-28; DCR, client pre-registration, and CIMD. Read more |
| Server Debugging | Manually run tools, resources, templates, prompts, and elicitation flows with full JSON-RPC logs. |
| Skills | Extend models with reusable behaviors in Playground. Local skills are read from your filesystem and never leave your machine; a project can also carry hosted skills, available on accounts where that is enabled. |