mcpx

MCPX is a token-efficient MCP client that discovers and interacts with MCP servers using TypeScript-first tool signatures. With MC PX, you can call tools using natural TypeScript-like syntax (for example, linear.createComment({ issueId: 'ENG-123', body: 'Great!' }) ) or use a structured data format to drive calls. The client also supports multi-line batch calls via stdin, and outputs in TOON by default to minimize token usage while staying friendly to LLMs. You can explore and invoke any MCP server you’ve configured on your system, including the Quick Start examples shown for popular services, and you can call ad-hoc endpoints directly without preconfiguring them, then persist them later if needed. MC PX emphasizes a friendly, code-style workflow: discover servers, call tools, and compose automations in TypeScript, all with automatic defaults, validation, and ergonomic helpers for results.

To use MC PX, start by listing your MCP servers or calling a specific tool. Use mcpx list to see configured servers, or mcpx list vercel to inspect a particular server’s tools in TypeScript-spec form. You can then call a tool either in function-signature form (server.tool({ args })) or in a data payload form ( { tool: 'server.tool', args: { ... } } ). The CLI supports multiple output formats (toon by default, with options for json, text, or raw) and can operate against ad-hoc endpoints via --http-url or --stdio. OAuth, stdio transports, and per-server configurations are managed automatically, with helpful flags to tailor behavior (like --config, --output, --env, and timeouts).

Examples include:

• Function call syntax: mcpx call 'linear.create_comment({ issueId: "ENG-123", body: "Great!" })'
• Data payload: mcpx call '{ tool: "linear.create_comment", args: { issueId: "ENG-123", body: "Great!" } }'
• Listing servers: mcpx list, mcpx list https://mcp.linear.app/mcp --all-parameters
• Ad-hoc server: mcpx call --stdio "bun run ./local-server.ts" --env TOKEN=xyz --persist config.json'

Prerequisites:

• A macOS or Linux environment with a modern Node.js toolchain (Node.js recommended; npm or bun can be used).
• Homebrew (on macOS) or your preferred package manager.

Install MC PX (via Homebrew):

1. Add the tap and install MC PX:

brew tap AIGC-Hackers/mcpx
brew install mcpx
# Or install in one command
brew install AIGC-Hackers/mcpx/mcpx

Run MC PX without installing (using bunx):

bunx mcpx list

Install via an alternate tap (if you follow Steipete’s packaging):

brew tap steipete/tap
brew install steipete/tap/mcpx

Notes:

• MC PX can run as a locally installed CLI or be invoked via bunx for quick exploration without a full install.
• The MCP config is typically stored under ./mcp.json and ~/.mcpx/mcp.json; MC PX can merge/auto-migrate these on first use.

If you’re on Windows, you can use WSL or a compatible environment to run the same Homebrew-based or bunx-based commands.

Tips and common scenarios:

• Auto-discovery: MC PX auto-discovers servers configured in Cursor, Claude Code/Desktop, Codex, or local overrides, and merges them into a unified mcp.json for reuse.
• Output formats: Default to TOON for token efficiency; switch to json/text/raw as needed with --output.
• Ad-hoc endpoints: You can point MC PX at any MCP endpoint using --http-url or --stdio, then persist the configuration later with --persist to reuse the signature.
• Authentication: OAuth is triggered automatically when required and cached for faster subsequent calls.
• Environment management: Use --env KEY=value to pass environment variables to ad-hoc servers; MC PX also supports --cwd for stdio-based transports.
• Data formats: Tools support both function-call syntax and structured data payloads (JSON5/TOML/YAML). JSON schemas are abstracted away in favor of TypeScript-style signatures.
• Timeouts and logging: Adjust timeouts with MCPX_LIST_TIMEOUT and MCPX_CALL_TIMEOUT; tail logs with --tail-log for easier debugging.