Prepare a Letter for Mailing with Grok and IRIS

Choose the Grok connector path, not an imaginary integration

This workflow concerns the Grok conversation product at grok.com. xAI documents custom MCP connectors under Grok Connectors: go to grok.com/connectors, choose New Connector and Custom, enter the server URL, and complete the supported authentication flow. On Grok Business or Enterprise, an administrator must provision the connector in the team cloud console first. IRIS is not listed among the built-in connectors in xAI’s documentation; do not assume it is already installed or authorized.

The xAI developer API at api.x.ai is a different route for building your own application with Grok models. An xAI API key is not an IRIS API key, and an API call to a Grok model does not connect a Grok consumer conversation to IRIS. If you only need an occasional letter, Grok can draft it while you independently export and review a final US Letter PDF for IRIS’s /letters/send flow; that does not require a connector.

• xAI: Grok Connectors ↗
• xAI: Grok Business and Enterprise connector management ↗
• IRIS: Upload and mail a reviewed PDF ↗

Connect only a reachable, appropriately scoped server

IRIS documents https://api.irispostalforms.com/mcp as a remote Streamable HTTP endpoint. Every MCP request needs an account-bound IRIS bearer API key with account:read. Preparation also needs documents:write for upload requests and registration, and mailings:read for quotes. Do not give a preparation connector mailings:write: that additional scope permits create-mailing, which charges credits and releases fulfillment.

xAI requires a custom MCP server to be reachable from Grok’s servers over the public internet; localhost and private-network addresses do not qualify. IRIS’s published HTTPS endpoint is the server URL, so no local tunnel is needed for that endpoint. Complete authentication only through a connector flow that actually supports the required Authorization: Bearer credential. xAI’s general connector instructions do not specify that every Grok account exposes arbitrary bearer-header configuration; verify the offered auth method before proceeding. If incompatible, use an organization-approved authenticated gateway or the separate IRIS website/REST workflow instead. Never place an API key in the URL, a chat prompt, browser code, a shared screenshot, or a public tunnel; a tunnel does not replace authentication.

• IRIS: MCP authentication and tool scopes ↗
• xAI: Custom MCP server reachability ↗
• Check the shared physical-mail MCP requirements ↗

Move the finished PDF with trusted local code

Finish the letter from verified facts and export a readable, unencrypted US Letter PDF. Open the final file and inspect every page. Grok’s conversation or an MCP create-document-upload result does not, by itself, transfer local PDF bytes to IRIS. From trusted software with access to the file, request a private upload using its exact filename, byte length, and kind letter; PUT those bytes to the returned uploadUrl within its expiry with every returned uploadHeaders value; verify that PUT succeeded; then register the returned key and save the immutable document ID. Do not send the IRIS bearer key to the storage upload URL, and keep the presigned URL private.

This local handoff can use IRIS REST even if Grok later uses the MCP quote-mailing tool. Give Grok only the registered document ID and the minimum approved address and options data needed to request a quote. A revised PDF is a different document: upload, register, quote, and review it again rather than reusing an earlier document ID or approval.

• IRIS: Private PDF uploads and registration ↗
• IRIS: OpenAPI contract ↗

Ask Grok for a quote, then stop

Supply a complete sender and recipient address from your authoritative records, the registered document ID, and explicit letter options. IRIS quote-mailing takes a complete mailing object and requires mailings:read. It returns a price in US cents; a quote does not spend credits, reserve that price, or submit mail. The following prompt is for preparation after the trusted PDF upload, not a command to read a local file or create an order.

Use the IRIS connector only to prepare one US letter mailing.
The final PDF has already been uploaded and registered by my trusted local workflow; its document ID is [REGISTERED_DOCUMENT_ID].
Use only the sender, recipient and letter options I explicitly provide. Do not invent or complete missing address fields.
Check the account balance and request a quote for the complete mailing object.
Show the document ID, both full addresses, all print options and quoted total in US cents for my review.
Do not call create-mailing, submit an order, or claim the letter has been sent. Stop and ask for human review.

• IRIS: MCP tools and quotation ↗

Make the paid mailing a separate human decision

Before submission, a person must open the actual PDF—not merely Grok’s summary—and verify every page, sender and recipient address, print options, current quote, and authority to send. Confirm available credits and correct any mismatch; obtain a fresh quote if the payload changes or submission is delayed. A successful quote is not permission to mail, and an estimated delivery date is not a guarantee.

Only after approval should a trusted submission workflow with mailings:write create the mailing using the exact approved payload and one durably saved idempotency key for that intended letter. Preserve the resulting order ID; if a response is uncertain, retry with the same key and unchanged payload rather than generating another key. Read status using the order ID instead of submitting again. A paid acknowledgement establishes an order, not delivery. Keeping the preparation connector without mailings:write makes the review boundary concrete.

• IRIS: Human review and submission ↗
• Handle uncertain responses without duplicate letters ↗