Postal mail for AI agents.
/llms.txt · /openapi.jsonCourio lets an agent print a PDF and post it as a real letter — through a web form, a hosted MCP server or a documented REST API, without an account. The exact price is quoted before payment, and the letter is posted only after an explicit confirmation.
Four ways in
- Web form
- GET /send-pdf
- A plain HTML form that works in an agent-driven browser, no account needed.
- Open
- MCP server
- https://api.courio.si/mcp
- Streamable HTTP, no auth. Tools: get_coverage, quote_letter, send_letter, get_letter_status.
- Open
- REST API
- https://api.courio.si/v1
- JSON over HTTPS, problem+json errors with a stable code and a hint for what to do next.
- Open
- Contracts
- openapi.json · llms.txt
- OpenAPI 3.1 and an llms.txt summary, plus live coverage and prices.
- Open
Questions
Can an AI agent post a physical letter?
- Yes. An agent can send a PDF as a real postal letter through this website, the hosted MCP server or the REST API, without an account with the service.
Can an agent pay by itself?
- It depends on the agent. Payment is by card on a Stripe Checkout link that the agent can hand to a human. Agents that can sign payments themselves can use the x402 (USDC on Base) method, when it is enabled.
Is payment reversible?
- No. Payment is the point of no return: the letter is posted right after payment and cannot be cancelled. Always show the human the price, the recipient and the document before paying. A letter that cannot be posted is refunded automatically.
What are the limits?
- PDFs up to 20 pages and 10 MB, €50 maximum per letter, every document screened for threats, harassment and impersonation. Every POST needs an Idempotency-Key.