Set up the PromptFax MCP connector

ChatGPT setup

ChatGPT MCP connector setup

In ChatGPT, custom MCP connectors are created from Settings -> Apps -> Create app. Use the values below to create a private PromptFax connector, review the discovered OAuth settings, and authorize PromptFax before starting a new chat.

ChatGPT steps

1. Open ChatGPT connector or app settings.

2. Create a custom MCP connector for PromptFax.

   

3. Set the MCP server URL to https://promptfax.app/mcp.

4. Choose OAuth authentication and complete authorization.

   

5. Refresh the connector so ChatGPT pulls the latest tool list.
6. Start a new chat and ask PromptFax to fax an attached document.
7. Confirm the composer attachment imports automatically. If it does not, use Choose PDF from ChatGPT in the widget.

Expected ChatGPT flow

ChatGPT should call start_session first and supply the official automatic files[] payload when available. PromptFax imports valid temporary download URLs immediately. The widget provides the picker fallback and owns destination entry, automatic quote creation, Stripe Checkout launch, and status polling. ChatGPT should not ask for a separate quote step after the widget already shows a price.

Payment opens through Stripe. PromptFax starts sending only after webhook-confirmed authorization; a browser redirect alone is not treated as payment truth.

Claude setup

Claude MCP connector setup

In Claude, remote MCP connectors are added from Customize -> Connectors -> Add connector -> Add custom connector. Use the PromptFax MCP server URL below. OAuth client ID and client secret are optional; PromptFax publishes the OAuth metadata Claude needs for the normal connection flow.

Claude steps

1. Open Claude Customize -> Connectors.

2. Choose Add connector -> Add custom connector.

   

3. Set the name to PromptFax and the remote MCP server URL to https://promptfax.app/mcp.

   

4. Leave optional OAuth client credentials blank unless Claude requires static credentials for your plan.
5. Save the connector, connect it, and complete the PromptFax OAuth flow.
6. Enable PromptFax for a new conversation from Claude's connector or tools menu.

Expected Claude flow

Claude should call start_session first. PromptFax advertises the neutral MCP App when Claude negotiates the standard UI extension, with a name-based compatibility path for older Claude clients. The app renders inline upload, destination, quote, payment-handoff, and status controls. Stripe Checkout still opens outside Claude because payment authorization remains a Stripe-hosted step.

Claude may list PromptFax tools before OAuth, but real workflow actions require authorization. Treat Claude file attachment behavior as host-specific and verify it with a non-sensitive sample PDF before using a real document. If Claude cannot render the inline app, use the PromptFax-hosted session page from the app or tool response as the fallback.

Claude tool permissions

Claude groups PromptFax tools from MCP metadata and its own permission model. Seeing start_session as interactive, get_status as read-only, and the document, quote, checkout, retry, send, and cancel tools as write/delete actions is expected. Leave approval enabled unless you intentionally want Claude to call fax workflow tools without checking with you first.

Other MCP clients

Generic MCP client setup

PromptFax also works with MCP clients that support remote Streamable HTTP servers and OAuth. Clients advertising the standard MCP Apps UI extension receive the inline PromptFax MCP App. Text-only clients use the hosted PromptFax session page or pass real HTTPS PDF URLs to fallback tools. Raw file IDs, attachment metadata, and local paths are not document inputs.

Connector values

MCP Server URL: https://promptfax.app/mcp

Transport: Streamable HTTP

Authentication: OAuth

OAuth discovery is automatic from the MCP server metadata.

Expected generic flow

1. Connect to https://promptfax.app/mcp using Streamable HTTP.
2. List tools; PromptFax allows anonymous discovery for directory and client probes.
3. Authorize before calling workflow tools such as start_session.
4. Start a session. Use the inline app when negotiated, or attach a PromptFax document or HTTPS PDF URL through the hosted fallback.
5. Use get_status to refresh the send workflow after payment, send, retry, or cancel actions.