v0.1.0

First release.

mcpsnoop is a transparent proxy for MCP. You wrap your server command with it; it forwards every byte to the real server untouched and shows the JSON-RPC going both ways in a terminal UI. The official Inspector connects as its own client, so it never sees the traffic between your real client (Claude Desktop, Cursor, Claude Code) and your server. mcpsnoop sits in that connection, so it does.

What you get:

• A live view of requests, responses, notifications and server stderr, with latencies and errors called out, including tool calls that come back with isError.
• Replay of a captured tool call against a fresh copy of the server, without driving the whole client again.
• The capabilities both sides negotiated at the handshake.
• Stream filtering (tool:, status:, dir:, kind:, id:) and search inside a frame.
• A live timer on pending calls, so a hung tool is obvious.
• stdio and streamable HTTP (JSON and SSE).
• A single static binary with no dependencies.

Install with go install github.com/kerlenton/mcpsnoop/cmd/mcpsnoop@latest, or download a prebuilt binary below. See the README for the demo.