MCPScope

Charles Proxy for AI tool calls. A local-first proxy that sits between an MCP client (Claude Desktop, or any agent) and its MCP servers, passively records every JSON-RPC message to SQLite, and shows a live terminal UI.

pip install mcpscope-cli

Why

• Watch your REAL agent, live. The MCP Inspector and similar tools are test harnesses: they are the client, poking your server by hand. MCPScope records what a running agent — Claude Desktop mid-conversation — actually does.
• History that outlives the session. Inspector history is React state; gone on reload. MCPScope stores every call from every session in local SQLite, so you can answer "what did my agent do last Tuesday?"
• Local-first, zero cloud, zero signup. Nothing leaves your machine. Free forever for single-user use.

Quickstart 1 — attach to Claude Desktop

mcpscope attach filesystem     # or any server name from your Claude Desktop config
# restart Claude Desktop, use it normally, then:
mcpscope ui --follow           # watch calls stream in live
mcpscope detach                # undo (config backup is made automatically)

attach rewrites that server's entry in claude_desktop_config.json (after backing it up) so Claude Desktop launches the server through the proxy. The agent and the server themselves are never modified.

Quickstart 2 — wrap any stdio MCP server

Wherever a client config says command: npx -y some-mcp-server, prefix it:

mcpscope run -- npx -y @modelcontextprotocol/server-filesystem ~/notes

stdin/stdout pass through byte-for-byte; a copy of each frame is parsed and recorded. The server's stderr also passes through untouched.

Quickstart 3 — proxy a remote (HTTP) MCP server

mcpscope run --http https://example.com/mcp --port 6280
# point your agent at http://127.0.0.1:6280/mcp instead of the upstream

Streamable HTTP (the current MCP remote transport) is forwarded verbatim, including SSE streams; request/response/SSE payloads are teed into the same store. Add --ui to get the TUI in the same terminal.

Browsing history

mcpscope sessions              # every recorded session, with call/error counts
mcpscope calls <session-id>    # one session's calls (--json for full frames)
mcpscope ui                    # TUI: arrows to inspect, / to filter, f to follow

Recordings live in ~/.mcpscope/mcpscope.db (override with --db or $MCPSCOPE_DB). It's plain SQLite — query it with anything.

What it is / what it is not

It is a passive observer for agents you run: a flight recorder for MCP traffic, with persistent history and a live UI.

It is not a test harness. It never calls your server on its own, never modifies messages, and has no "send request" button — that's the official MCP Inspector, which is great at what it does. Run both.

Guarantees the design enforces:

• Pass-through is sacred: bytes are forwarded verbatim; parsing happens on a copy, for logging only. Malformed or unknown messages are never dropped, altered, or reordered — they're recorded raw.
• Recording never blocks the proxy path (write-behind queue; under extreme pressure it drops log entries, counted, never traffic).
• Protocol-churn insurance: messages are interpreted, never gated. New spec revisions flow through untouched.

License

Apache-2.0.