Add the SendFaxFast connector to your AI assistant, then tell it the fax number. The AI gives you a secure upload link for your PDF, JPG or PNG. In ChatGPT on the web, you can usually attach the file directly. You pay per fax through a Stripe payment link, or use prepaid AI fax credits starting at $11.99 for 5 faxes.
You already ask your AI assistant to write letters and fill in forms. With the SendFaxFast connector, it can also send the finished document as a real fax. Here is how it works in Claude, ChatGPT and Grok, what it costs, and what to watch out for.
What does "faxing with AI" actually mean?
Claude, ChatGPT and Grok can connect to outside services through so-called custom connectors (based on the Model Context Protocol, or MCP). Once you add the SendFaxFast connector, your AI assistant can:
- check the price of a fax before anything is sent,
- give you a secure link to upload your document,
- send the fax after you confirm the number,
- check whether the fax was delivered.
The fax itself goes out through the same system as a fax sent on sendfaxfast.com. The AI only handles the conversation for you.
What do you need?
- An AI app that supports custom connectors: Claude (web or desktop app), Grok on grok.com, or ChatGPT on the web with Developer mode. Some ChatGPT plans only allow read-only tools, so sending may not be available on every plan.
- Your document as a PDF, JPG or PNG, up to 10 MB.
- The recipient's fax number including the country code, for example +1 for the US and Canada.
Pay per fax or AI fax credits?
There are two ways to pay. Neither one is a subscription.
| Pay per fax | AI fax credits | |
|---|---|---|
| Connector URL | https://sendfaxfast.com/api/mcp.php | Your personal URL from the credits email |
| How you pay | The AI shows a Stripe payment link for each fax | 1 credit is deducted per fax |
| Price | Same as the website, from $2.49 | 5 for $11.99, 10 for $19.99, 20 for $34.99 |
| Best for | A one-time fax | Several faxes, no payment step each time |
With credits, 1 credit covers 1 complete fax of up to 100 pages, and credits never expire. After you buy a package on the AI fax credits page, your API key and your personal connector URL arrive by email. That URL contains your key, so keep it private: anyone who has it can use your credits.
How do I add the connector?
Claude
In Claude (web or desktop app), open Customize → Connectors → Add custom connector, paste the connector URL and click Add.
Grok
Go to grok.com/connectors → New Connector → Custom and paste the connector URL.
ChatGPT
On the web, turn on Developer mode under Settings → Apps → Advanced settings. Then create a new app with the connector URL and choose No authentication.
How do I send a document from the chat?
- Tell the AI what you want. For example: "I want to fax a document to +1 212 555 0100."
- Upload your file. The AI shows you a personal upload link. Open it on your phone or computer and choose your PDF, JPG or PNG. On a phone you can also take a photo of the paper. Photos are turned into fax pages automatically. The link is valid for 30 minutes.
- Go back to the chat and say: "Done – please send the fax."
- Check the fax number. Read the number the AI repeats back to you before you confirm. With pay per fax, you then pay through the Stripe link. With credits, the fax goes out right away.
- Wait for the email. You get an email when the fax is delivered.
In ChatGPT on the web you can usually skip step 2: attach the file to your message and the connector picks it up. If that doesn't work in your app, ChatGPT falls back to the upload link. Claude and Grok don't pass chat attachments to connectors, so there the upload link is the way to go.
If your PDF is already online, you can also give the AI a direct, public https link to it, for example: "Fax the PDF at https://example.com/letter.pdf to +1 212 555 0100."
What does it cost?
With pay per fax, the AI uses the same prices as the website:
| Fax type | Pages | Price (USD) |
|---|---|---|
| Short fax | 1–5 | $2.49 |
| Long fax | 6–20 | $3.49 |
| XL fax | 21–40 | $4.99 |
| XL Fax Plus | 41–100 | from $6.24 |
Prices per fax as of October 2026, the same for the US & Canada (+1), Australia (+61), New Zealand (+64), and 39 more supported countries. XL Fax Plus costs $4.99 plus $1.25 for each started 10 pages beyond 40. Maximum 100 pages per fax. Single faxes need no account and no subscription.
With AI fax credits, each fax costs 1 credit, no matter how many pages it has (up to 100). That works out to $2.40, $2.00 or $1.75 per fax, depending on the package.
What happens if the fax fails?
If a fax paid with credits can't be delivered, the credit is refunded automatically. For pay per fax, you get a full refund if the fax can't be delivered after all retries, as described in our refund policy.
Each upload link can be used for one fax. If a send fails, ask the AI for a new link and upload the file again. That way the same document is never faxed twice by mistake.
Is it safe to fax through an AI assistant?
- Your file goes straight to SendFaxFast. With the upload link, the document is uploaded to sendfaxfast.com, not into the chat. Uploaded files are deleted after they are used or when the link expires.
- Your chat is still a chat. Anything you type into the conversation is handled under your AI provider's privacy terms. Keep sensitive details in the document, not in your messages.
- Keep your connector URL private if you use credits, because it contains your key.
- Always check the number. A wrong digit sends your document to a stranger.
Sending health information? Read Is online fax HIPAA compliant? first.
Frequently asked questions
Can I attach a PDF directly in Claude or Grok?
Not at the moment. Claude and Grok don't pass files from the chat to connectors. Instead, the AI gives you a secure upload link. Open it, upload your PDF, JPG or PNG, and tell the AI you're done.
Do I need an account or a subscription?
No. For pay per fax, you add the connector and pay each fax through a Stripe link. AI fax credits are a one-time purchase, and the credits never expire.
How many pages does one AI fax credit cover?
1 credit covers 1 complete fax of up to 100 pages. There is no extra charge per page.
How do I know the fax was delivered?
You get an email when the fax is delivered. You can also ask your AI assistant: "Has my fax been delivered?"
Can the AI send my fax later?
Yes. Tell the AI the date and time, for example "send it tomorrow at 9 AM New York time," and it schedules the fax.