Send a letter from Cline.

Add paperplane to Cline’s MCP settings and it can quote and send a real USPS letter — no account required, free sandbox mode included.

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

Set it up in Cline

Step 1

Add via Cline’s MCP settings

"type" must be exactly "streamableHttp" (camelCase) — "http" or a missing type falls back to legacy SSE and gets a 405.

{
  "mcpServers": {
    "paperplane": {
      "type": "streamableHttp",
      "url": "https://sendpaperplane.com/api/mcp"
    }
  }
}

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 Cline? 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": {
    "paperplane": {
      "type": "streamableHttp",
      "url": "https://sendpaperplane.com/api/mcp"
    }
  }
}

All agents · API docs

Common questions

Why does the config specify "streamableHttp" exactly?

Cline requires the exact camelCase string "streamableHttp" — "http", or a missing type, falls back to legacy SSE and gets a 405 against this endpoint.

What tools does Cline 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. Every quote shows the exact total before you approve anything, and sandbox mode is free.