Mcp Debug

MCP Debug

[](https://goreportcard.com/report/github.com/giantswarm/mcp-debug)

mcp-debug is a command-line tool for debugging MCP (Model Context Protocol) servers. It helps developers inspect MCP server capabilities, debug tool integrations, and test server notifications.

Key Features

• Connect to any MCP Server: Works with servers using streamable-http transport.
• OAuth 2.1 Authentication: Full MCP authorization specification (2025-11-25) compliance with security-first defaults
• Automatic discovery (RFC 9728 Protected Resource Metadata, RFC 8414 AS Metadata)
• Resource Indicators (RFC 8707) for token audience binding
• PKCE validation (required by MCP spec)
• Dynamic Client Registration (RFC 7591) and Client ID Metadata Documents
• Step-up authorization for runtime permission escalation
• Intelligent scope selection (auto and manual modes)
• Interactive REPL: Explore available tools, resources, and prompts interactively.
• MCP Server Mode: Acts as an MCP server itself, allowing integration with AI assistants like Cursor.
• Verbose Logging: Detailed logging of JSON-RPC messages for in-depth debugging.
• Self-Update: Keep the tool up-to-date with a single command.
• Shell Autocompletion: Generates autocompletion scripts for Bash, Zsh, Fish, and PowerShell.

Getting Started

Installation

To build the tool from source and install it in your PATH:

go install github.com/giantswarm/mcp-debug@latest

Documentation

For detailed instructions on all features:

• [➡️ mcp-debug Usage Guide](./docs/usage.md) - Complete feature guide
• [➡️ OAuth 2.1 Documentation](./docs/oauth/) - Comprehensive OAuth authentication guide

OAuth 2.1 Quick Start

Connect to a protected MCP server with automatic discovery:

./mcp-debug --oauth --endpoint https://mcp.example.com/mcp

This automatically:

• Discovers the authorization server (RFC 9728)
• Validates PKCE support (required by MCP spec)
• Uses the official Client ID Metadata Document (CIMD)
• Falls back to Dynamic Client Registration if CIMD is not supported
• Opens your browser for authorization
• Connects with audience-bound tokens (RFC 8707)

Client ID Metadata Document (CIMD)

mcp-debug uses CIMD by default for OAuth authentication. The official client metadata is hosted at:

https://giantswarm.github.io/mcp-debug/client.json

This allows OAuth-protected MCP servers to identify mcp-debug without requiring pre-registration. The authorization server fetches the metadata from this URL and displays "MCP Debugger CLI" on the consent screen.

If you need to use a custom CIMD or disable it:

# Use a custom CIMD URL
./mcp-debug --oauth --oauth-client-id-metadata-url https://example.com/my-client.json --endpoint https://mcp.example.com/mcp

# Disable CIMD and force Dynamic Client Registration
./mcp-debug --oauth --oauth-disable-cimd --endpoint https://mcp.example.com/mcp

See the [OAuth Documentation](./docs/oauth/) for detailed guides, examples, and troubleshooting.

Basic Examples

Connect to a server and listen for notifications:

./mcp-debug --endpoint http://localhost:8090/mcp

Start the interactive REPL:

./mcp-debug --repl

Run as an MCP server for AI assistant integration:

./mcp-debug --mcp-server

Refer to the [usage guide](./docs/usage.md) for more advanced examples.

Contributing

Contributions are welcome! Please open an issue or submit a pull request.

License

mcp-debug is licensed under the Apache 2.0 License.

Source & license

This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: giantswarm
• Source: giantswarm/mcp-debug
• License: Apache-2.0

Install and usage instructions live in the source repository linked above.