Send a letter from Grok Build CLI.

Grok Build CLI reuses Claude Code’s MCP config format directly — add paperplane the same way and it can quote and send a real USPS letter.

Free to preview — see the exact PDF before you pay. Sending starts at $1.99, no account required.

Set it up in Grok Build CLI

Step 1

Same format as Claude Code

Reuses Claude Code’s .mcp.json format directly — see that tab. New (2026) product; treat as provisional.

Try it: free, nothing mailed

Tell your agent:

Using the paperplane tools, quote a 1-page certified letter to Property LLC, 1 Main St, Richmond VA 23220, then send it in sandbox mode.

Not on Grok Build CLI? Any surface works.

The same three calls from the CLI, any MCP client or plain REST. Sandbox is free and mails nothing.

Send a letter

{
  "mcpServers": {
    "mail": { "url": "https://sendpaperplane.com/api/mcp" }
  }
}

All agents · API docs

Common questions

Does Grok Build CLI have its own config format?

No — it reuses Claude Code’s .mcp.json / claude_desktop_config.json shape directly. It’s a new (2026) product, so treat the format as provisional and re-check this page if it stops working.

What tools does it get?

quote_letter, send_letter, and get_letter_status for mailing, plus buy_credits for pre-funding sends. Postcards are live (from $1.99) via the REST API’s format field, though not yet an MCP tool argument.

How much does sending cost?

Letters start at $1.99 for First-Class; Certified Mail starts at $12.99. Sandbox mode is free.