mcpobs

Local-first proxy and trace viewer for the Model Context Protocol. See every JSON-RPC message your AI agents send.

Drop it between your MCP client (Claude Desktop, Cursor, Cline, Continue, Windsurf) and your servers. Every message lands in a real-time timeline you can replay and diff.

Install

npm install -g @vnmoorthy/mcpobs

The CLI command is mcpobs (the npm name is scoped because the unscoped mcpobs collides with an unrelated package).

This downloads the prebuilt binary for your platform from the matching GitHub release and verifies its sha256.

Supported platforms: macOS arm64/x64, Linux arm64/x64, Windows x64.

Quickstart

mcpobs init                                                   # ~/.mcpobs/config.toml
mcpobs start &                                                # daemon on :7890
mcpobs add filesystem --command npx \
  --args '@modelcontextprotocol/server-filesystem,/Users/me'  # add an upstream
open http://localhost:7890                                    # browser UI

Links

• Source: https://github.com/vnmoorthy/mcpobservatory
• Issues: https://github.com/vnmoorthy/mcpobservatory/issues
• License: Apache-2.0

Troubleshooting

mcpobs: binary not found — install completed but the postinstall step was skipped (e.g. --ignore-scripts). Re-install: npm install -g @vnmoorthy/mcpobs.

mcpobs: unsupported platform — only the platforms listed above ship prebuilts. File an issue with your uname -a.

Behind a firewall — set MCPOBS_REPO=your/mirror in the environment before install to point at a release mirror.

Skip download — set MCPOBS_SKIP_DOWNLOAD=1 in CI to skip the binary download (use the binary you provided yourself in node_modules/mcpobs/bin/).