app.promptfax/promptfax

Official8 tools

PromptFax

Send a one-off fax from inside ChatGPT or Claude. Pay-per-use, $2-$4.50 per delivered fax.

Send faxes from ChatGPT or Claude with pay-per-use pricing ($2-$4.50).

Captured live from the server via tools/list.

start_session

Use this first when a user wants to send or price a fax. PromptFax is built for irregular, pay-per-use outbound faxing: every real send requires a user-reviewed quote and Stripe payment authorization before transmission. MCP clients should set hostType to identify their host: chatgpt, claude, browser, or other. When calling this from ChatGPT, set hostType to chatgpt so PromptFax uses the ChatGPT widget and file flow. In ChatGPT, this opens the PromptFax widget; after the widget is shown, let the widget handle file selection, destination entry, automatic quote creation, Stripe Checkout, and status tracking. If no document is attached, tell the user to attach a document in the widget. The widget does not provide a document preview step. Do not tell ChatGPT users to get a quote; after the widget has a document and valid destination, tell them to verify the price and use Pay & send when ready. For Claude and other MCP hosts that cannot pass files directly, use the agent-friendly hosted PromptFax session page to guide upload/review, request a quote, launch Stripe Checkout, and poll delivery status. Do not call get_quote, checkout, or send_fax for a ChatGPT widget session unless the user explicitly asks for fallback behavior or the widget is unavailable. Use get_status only for a textual status refresh.

Parameters (6)

sessionIdstring
PromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.
faxNumberstring
Destination US fax number. Accepts common human formats such as 415-555-0182 or E.164 format such as +14155550182.
hostTypestring
Identify the MCP host so PromptFax can choose the right interaction mode. Use chatgpt for ChatGPT, claude for Claude, browser for a browser-hosted app, or other for unknown clients.
hostCapabilitiesobject
Optional host capability hints, such as whether the client supports widgets, file-picking, hosted links, or other interactive surfaces.
filesarray
Optional host-supplied files for initial attachment. ChatGPT may provide temporary download URLs in files[].download_url.
metadataobject
Optional host-specific metadata for diagnostics or session continuity.

attach_document

Fallback/non-widget tool for binding a PromptFax document or one or more HTTPS PDF URLs into the current MCP session before requesting a quote. In ChatGPT widget sessions, prefer the widget's file controls after start_session instead of calling this tool unless the widget is unavailable or the user explicitly asks for fallback behavior.

Parameters (3)

sessionIdstringrequired
PromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.
documentIdstring
PromptFax document identifier created by a prior upload or hosted session.
fileUrlsarray
One or more HTTPS URLs for PDF or image documents that PromptFax should attach to the fax workflow.

get_quote

Fallback/non-widget tool for creating a user-reviewable pay-per-use fax quote when you have a fax number and either an MCP session, a PromptFax documentId, or one or more HTTPS PDF URLs. A quote is required before Stripe Checkout and before any real fax transmission. In ChatGPT widget sessions, do not call this after start_session because the widget auto-quotes once the document and destination are ready.

Parameters (4)

sessionIdstring
PromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.
faxNumberstring
Destination US fax number. Accepts common human formats such as 415-555-0182 or E.164 format such as +14155550182.
fileUrlsarray
One or more HTTPS URLs for PDF or image documents that PromptFax should attach to the fax workflow.
documentIdstring
PromptFax document identifier created by a prior upload or hosted session.

checkout

Fallback/non-widget tool for starting external Stripe Checkout after the user accepts a pay-per-use quote. Payment authorization is required before PromptFax can send; PromptFax treats webhook-confirmed authorization, not browser redirect, as payment truth. In ChatGPT widget sessions, do not call this after start_session because the widget's Pay & send step opens Checkout.

Parameters (3)

sessionIdstring
PromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.
sendIntentIdstring
PromptFax send intent identifier returned by get_quote or session status. Use this for checkout, send, status, retry, or cancel operations.
autoSendAfterAuthorizationboolean
When true, PromptFax sends automatically after Stripe confirms payment authorization. When false, call send_fax after authorization.

send_fax

Fallback/non-widget tool for sending after payment is authorized and the user explicitly wants to send now. In ChatGPT widget sessions, do not call this after start_session unless the widget is unavailable or the user explicitly asks for fallback behavior.

Parameters (2)

sessionIdstring
PromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.
sendIntentIdstring
PromptFax send intent identifier returned by get_quote or session status. Use this for checkout, send, status, retry, or cancel operations.

get_status

Use this when you need the latest PromptFax workflow state, quote/payment state, or fax transmission status.

Parameters (2)

sessionIdstring
PromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.
sendIntentIdstring
PromptFax send intent identifier returned by get_quote or session status. Use this for checkout, send, status, retry, or cancel operations.

retry_failed_fax

Use this after a retry-eligible failed fax to prepare a new authorization attempt.

Parameters (2)

sessionIdstring
PromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.
sendIntentIdstring
PromptFax send intent identifier returned by get_quote or session status. Use this for checkout, send, status, retry, or cancel operations.

cancel

Use this when you need to cancel the active PromptFax send.

Parameters (2)

sessionIdstring
PromptFax MCP session identifier returned by start_session. Use this to continue a session-backed fax workflow.
sendIntentIdstring
PromptFax send intent identifier returned by get_quote or session status. Use this for checkout, send, status, retry, or cancel operations.

Install

claude_desktop_config.json

{
  "mcpServers": {
    "promptfax": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-remote",
        "https://promptfax.app/mcp"
      ]
    }
  }
}

Desktop config is stdio-only; this bridges via mcp-remote. Native remote: Settings > Connectors.