MCPJam Inspector is a testing and evaluation platform for developers building Model Context Protocol (MCP) servers, MCP apps, and ChatGPT apps. Different clients such as ChatGPT, Claude, and Cursor read a server differently; the inspector emulates those clients, exposes every JSON-RPC message and OAuth exchange, and runs evals so you can see where a server breaks and track accuracy over time.
It runs three ways: a hosted web app at app.mcpjam.com (HTTPS servers only, shareable server links), a desktop app for Mac and Windows, or npx @mcpjam/inspector@latest in the terminal (Node.js 20+). The desktop and terminal versions also support local STDIO servers, tunneling, skills, and tasks. A Docker build from source binds to localhost on port 6274.
Features
- Playground: a cross-client chat interface that emulates UIs, tool calls, and skills with Chat, Trace, and Raw views, including OpenAI Apps SDK and MCP app widgets in a DevTools-style emulator with Desktop, Tablet, and Mobile modes, locale, CSP, theme, and safe-area testing
- Chat: multi-server chat on frontier models for free or with your own API key, comparing up to three models side by side with per-server token usage
- OAuth debugger: step-by-step visualization of OAuth and EMA flows with guided conformance checks across spec versions 2025-03-26, 2025-06-18, 2025-11-25, and the 2026-07-28 draft, including DCR, client pre-registration, and CIMD
- Server debugging: manual runs of tools, resources, resource templates, prompts, and elicitation flows with full JSON-RPC logs
- Skills: reusable model behaviors loaded from the local filesystem, with hosted skills on accounts where enabled
- Workspaces: shared server groups with real-time team sync
- Evals: test cases with expected tool calls run across LLMs, with accuracy, latency, and tool-call metrics over time
- CLI: probe servers, run doctor checks, exercise OAuth, and list tools, resources, and prompts from the shell
- SDK: programmatic inspections, capability snapshots, and assertions on tool and resource shapes
- CI/CD: conformance, end-to-end tests, evals, and OAuth checks on every pull request in GitHub Actions, GitLab CI, or other pipelines
- Coverage: 16 client configurations and 170+ models
