MCP Workbench – Visual Debugger for MCP Servers

TL;DR

TL;DR: MCP Workbench is a free browser-based visual debugger for Model Context Protocol servers — inspect JSON-RPC traffic, test tools and resources, and explore server capabilities without writing a single line of code.

What Is MCP Workbench?

MCP Workbench is a web-based visual debugger and test client for servers built on the Model Context Protocol (MCP). It lets developers inspect the JSON-RPC communication between an LLM client and an MCP server, execute tool calls, browse resources, and monitor prompts in real time — all from a clean UI.

The tool is developed by Orkes, the company behind the Conductor workflow engine. It is free to use and runs entirely in the browser with no local install required.

Key features

• Real-time JSON-RPC inspector — watch every request and response between client and server
• Tool explorer — call any MCP tool with a form-based interface, inspect responses
• Resource browser — read resources exposed by the server with content-type filtering
• Prompt viewer — list and sample prompts the server exposes
• OAuth support — authenticate against servers that require OAuth
• Streamable HTTP transport — connects to MCP servers over Streamable HTTP, the protocol’s recommended transport

Setup Workflow

MCP Workbench requires no installation. Open mcp-workbench.ai in a browser.

Step 1: Connect an MCP server

On the left panel, click “Select MCP Server” and choose from available presets (Anthropic Claude, Filesystem, GitHub, etc.) or add a custom server URL.

For a custom server, enter the server’s Streamable HTTP endpoint. The UI will attempt to initialize the connection and list available capabilities.

Step 2: Inspect the protocol handshake

Once connected, the main panel displays the JSON-RPC handshake — initialize, tools/list, resources/list, and prompts/list calls appear as a readable transaction log. Click any entry to expand the full request and response bodies.

Step 3: Test a tool

Switch to the Tools tab. Select a tool from the list (e.g., github_tools::list_repos). Fill in the arguments using the generated form and click Run. The response appears below, formatted as JSON with syntax highlighting.

Step 4: Browse resources

Switch to the Resources tab. Click any resource URI to fetch its current content. Content-type filtering is available for servers that expose multiple representations.

Source and Accuracy Notes

• Project page: mcp-workbench.ai
• Author: Orkes, Inc.
• License: Proprietary free-to-use (no open-source license found; no public GitHub repository)
• HN launch thread: news.ycombinator.com/item?id=46532597
• Source last checked: 2026-08-13

Practical Evaluation Checklist

• Does it connect to a local MCP server? Yes — enter the server URL directly
• Is the JSON-RPC inspector readable? Yes — request/response bodies are syntax-highlighted
• Can you call tools without writing code? Yes — form-based tool execution
• Does it support OAuth servers? Yes — OAuth flow is built in
• Is a local install required? No — fully browser-based
• Is it free? Yes — no pricing tier observed

Security Notes

MCP Workbench is a client-side-only web app. All protocol traffic runs between your browser and the MCP server you connect to — no data is proxied through Orkes’ infrastructure. However:

• Only connect to trusted MCP servers — the tool executes tools on your behalf
• OAuth tokens are stored in browser memory only and are not persisted
• If self-hosting an MCP server, ensure the Workbench URL is allowed under your server’s CORS policy

FAQ

Q: Is MCP Workbench open source? A: No public source repository was found. It is a free web application from Orkes, Inc.

Q: Does it work with any MCP server? A: It implements the MCP client side over Streamable HTTP. Servers that use a different transport (e.g., stdio-only servers) will require a proxy or adapter.

Q: Can I inspect traffic from a local server behind a firewall? A: Yes — since the browser connects directly to the server’s HTTP endpoint, it works with local servers as long as the browser can reach the endpoint.

Q: Is my data sent to Orkes? A: No. MCP Workbench is a pure client-side tool. All JSON-RPC traffic stays between your browser and the target server.

Conclusion

MCP Workbench fills a practical gap in the MCP ecosystem: a zero-install, visual way to debug and test MCP servers. Whether you are building a new MCP server, evaluating an existing one, or just exploring how the protocol works, the live JSON-RPC inspector alone is worth the bookmark. The form-based tool executor and resource browser round out a focused, well-scoped tool that every MCP developer should have in their browser tabs.