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PostAgent
**PostAgent lets an AI agent send real, physical mail.** Upload a document, lock a price quote, pay per send, and PostAgent prints it and ships it via USPS. Built for autonomous agents: **pay per call in USDC on Base via the [x402](https://www.x402.org/) protocol** or credit cards, no signup, no human-issued API key, no billing account. ### What it does - **Letters** — PDF, HTML, Markdown, text, DOCX, or image; black & white or color. Optional **certified, certified-with-return-receipt, or registered** mail for proof of delivery. - **Postcards** — 4×6, 6×9, 6×11, full color from front/back a
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Available tools
create_letter
Upload and normalize a FINISHED, ready-to-mail document to PDF. Choose this when the content is final and IDENTICAL for every recipient — including when you mail the same letter to many people (just quote/pay once per recipient with the same documentId). The exact bytes you give are what gets printed. Use create_template instead only when the content must vary per recipient via {{fields}}. Returns a documentId, the stored page count, byte size, and source format. Free; no payment required. Provide the document EXACTLY ONE way: `content` (inline text, for html/markdown/text), `contentBase64` (base64-encoded binary, for pdf/docx/image), or `url` (a publicly reachable URL the server fetches). Supplying none, or more than one, is an error. Maximum upload size is 31457280 bytes (~30 MB); output page size is US Letter. Any `{{...}}` text is printed LITERALLY here — it is NOT treated as a merge field. If you want personalized mail merge across recipients, use `create_template` instead. Reserved address zone: a recipient address block is printed over the top ~3 inches of page 1, so the server reserves that space for you automatically. For text/html/markdown/docx, page-1 content is pushed below the block (content may therefore flow onto an additional page); for pdf and image inputs, a blank first page is prepended. As a result the returned page count — and the per-page price in the resulting quote — can be one more than your source document (e.g. a single-page PDF is stored as 2 pages). You do NOT need to leave the top of your document blank yourself. See the postagent://formats resource for per-format details.
create_template
Upload a REUSABLE template containing `{{field}}` placeholders (e.g. `Dear {{name}},` or `Balance due: {{amount}}`). Choose this ONLY when the content must vary per recipient (mail merge) — recipient count is irrelevant, so a single personalized letter belongs here too. If the content is identical for everyone, use create_letter instead (this tool rejects input with no `{{fields}}`). Returns a documentId with `kind: "html_template"`, a `mergeFields` list of the detected field names, and an `estimatedPageCount`. Free; no payment required. Template source must be TEXT-BASED (html, markdown, or text) and must contain at least one `{{field}}`, or the upload is rejected — for a finished document with no merge fields, use `create_letter`. Provide the template EXACTLY ONE way: `content` (inline text), `contentBase64` (base64-encoded text), or `url` (a publicly reachable URL the server fetches). Supplying none, or more than one, is an error. Maximum upload size is 31457280 bytes (~30 MB); output page size is US Letter. Reuse one template documentId across recipients: call create_mail_quote ONCE PER RECIPIENT, supplying that recipient's values via `mergeVariables` (every field in `mergeFields` must have a non-empty value). The server substitutes the values and renders that recipient's personalized PDF at quote time, so `estimatedPageCount` is only a baseline — the binding page count and price are set per quote from the actual rendered output. Reserved address zone: a recipient address block is printed over the top ~3 inches of page 1, so the server reserves that space automatically (page-1 content is pushed below the block and may flow onto an additional page). You do NOT need to leave the top blank yourself. See the postagent://formats resource for details.