# Oh Fax

> Outbound fax for the United States and Canada. Quote a PDF + number, pay once, get a delivery receipt. Designed for agents (MPP / MCP), developers (REST / CLI), and humans (browser).

Product site: https://ohfax.com
App / API host: https://app.ohfax.com
OpenAPI (MPP discovery): https://app.ohfax.com/openapi.json
MCP: https://app.ohfax.com/mcp
Human docs: https://ohfax.com/docs

Agents pay via MPP — no Oh Fax account required. An MPP-capable payer (`mppx` or an agent wallet) is required.

## When to use Oh Fax

Use Oh Fax to send a signed lease, court form, insurance claim, or W-9 to a US/CA fax number when email is not accepted. The agent has a PDF and an E.164 destination number and needs a delivery receipt.

## Critical rules for agents

1. **Always quote before you send.** Quoting is free and sends nothing. The quote returns the binding price and a `quote_id`.
2. **The binding amount is the HTTP 402 challenge** (or MCP payment meta) on `POST /pay`, not a guessed formula and not an OpenAPI floor example.
3. **Agents need no Oh Fax account and no API key** when paying via Machine Payments Protocol (MPP). An MPP-capable payer (`mppx` or an agent wallet) is required. Prepaid API keys are an optional developer path.
4. **Destinations: US and Canada only.** PDF only, max 10 MB / 30 pages. Outbound only (no inbound fax).
5. **Currency: USD.** $1.00 per fax up to 25 pages, 2¢ per page after that (card); 2¢ per page from a prepaid balance or MPP stablecoin. See https://ohfax.com/pricing. Confirm via quote before paying.
6. **Idempotency:** every REST send requires an `Idempotency-Key` so retries cannot double-charge or double-send.
7. **Undeliverable faxes are refunded in full** (busy, no answer, not a fax). Delivered faxes are not refundable.

## Fastest path for agents (recommended)

### A. MCP (preferred)

**Claude Code**

```
claude mcp add --transport http ohfax https://app.ohfax.com/mcp
```

**Cursor** — `.cursor/mcp.json` or Settings → MCP:

```json
{
  "mcpServers": {
    "ohfax": {
      "url": "https://app.ohfax.com/mcp"
    }
  }
}
```

**Codex**:

```sh
codex mcp add ohfax --url https://app.ohfax.com/mcp
```

Manual config: set `url = "https://app.ohfax.com/mcp"` under `[mcp_servers.ohfax]` in `~/.codex/config.toml`. Remote URL: https://app.ohfax.com/mcp (streamable HTTP).

**Muse Code** — `~/.config/muse/settings.json`:

```json
{
  "schema_version": 1,
  "mcp_servers": {
    "ohfax": {
      "transport": "streamable_http",
      "url": "https://app.ohfax.com/mcp",
      "mode": "optional"
    }
  }
}
```

**Any MCP client:** remote URL https://app.ohfax.com/mcp (streamable HTTP; no API key for the MPP path). Payment requires an MPP-capable payer (`mppx` or an agent wallet).

Tools (call in order):

| Tool | Purpose | Notes |
|------|---------|-------|
| `quote_fax` | Price + validate | Free. Inputs: `to`, and either `document_url` or `document_base64`. Returns `quote_id`, pages, amount. |
| `send_fax` | Get payment authorization for a quote | Input: `quote_id`. Does **not** charge by itself. |
| *(pay)* | Satisfy MPP / HTTP 402 on `/pay` | No Oh Fax account. Use MPP-capable client (`mppx`, agent wallet, etc.). |
| `get_fax_status` | Poll delivery | Statuses include awaiting_payment, paid, submitting, submitted, sending, delivered, failed, refunded. |
| `get_fax_receipt` | Final receipt | Available once the fax is final. |

Payment is still MPP — no Oh Fax account required; use an MPP-capable payer.

### B. HTTP + MPP (no MCP client)

1. `POST https://app.ohfax.com/api/v1/quotes` with multipart form: `to`, `file` (PDF). Free.
2. Read `quote_id` and exact `amount` from the response.
3. `POST https://app.ohfax.com/pay?quote_id=…` (or body with `quote_id`). Unpaid → **HTTP 402** with MPP challenge.
4. Complete payment with an MPP client; binding amount is the challenge.
5. Poll `GET https://app.ohfax.com/api/v1/faxes/{fax_id}` then receipt when final.

Discover payment terms: `GET https://app.ohfax.com/openapi.json`.

## Developer path (prepaid balance)

1. Google sign-in at https://app.ohfax.com/account
2. Top up ($5 / $10 / $25 / $50), create API key (`afx_live_…` shown once)
3. Quote free; send with `Authorization: Bearer …` + `Idempotency-Key`
4. Optional CLI: `ohfax` with `OHFAX_API_KEY` and `OHFAX_URL=https://app.ohfax.com`

See https://ohfax.com/docs/api and https://ohfax.com/docs/cli

## Pricing examples

| Pages | Card | Prepaid balance | MPP stablecoin |
|------:|-----:|----------------:|---------------:|
| 1 | $1.00 | $0.02 | $0.02 |
| 3 | $1.00 | $0.06 | $0.06 |
| 5 | $1.00 | $0.10 | $0.10 |
| 10 | $1.00 | $0.20 | $0.20 |
| 30 (max) | $1.10 | $0.60 | $0.60 |

## What success looks like

- Delivery usually within a few minutes of payment.
- Track on status endpoint or browser `https://app.ohfax.com/f/:id`.
- Document bytes deleted ~24h after a final state; transaction metadata (destination, pages, timing, content hash) retained — contents are not.
- Webhooks (account holders): `fax.delivered` / `fax.failed` with `x-ohfax-event`, `x-ohfax-signature`, `x-ohfax-delivery-id`. Docs: https://ohfax.com/docs/webhooks

## Docs map

- Overview: https://ohfax.com/docs
- Pricing: https://ohfax.com/pricing
- Compare: https://ohfax.com/compare
- Quickstart: https://ohfax.com/docs/quickstart
- API: https://ohfax.com/docs/api
- MCP: https://ohfax.com/docs/mcp
- CLI: https://ohfax.com/docs/cli
- Webhooks: https://ohfax.com/docs/webhooks
- Limits & acceptable use: https://ohfax.com/docs/limits
- Privacy: https://ohfax.com/privacy
- Terms: https://ohfax.com/terms
- MPP protocol docs (for payment clients): https://mpp.dev/llms.txt

## Do not

- Skip quoting and invent a price.
- Retry a paid send without a stable idempotency key (REST).
- Fax outside US/CA, non-PDF, or >30 pages / >10 MB.
- Send bulk/unsolicited advertising or premium-rate numbers.
- Expect inbound fax receiving (not offered).

## Contact

Product questions / billing disputes: support@ohfax.com

## Pages

- [Oh Fax — Send a fax from your browser](https://ohfax.com/): Send a PDF to any fax number in the US or Canada from your browser. See the exact price before you pay. No account, no subscription. (Markdown: https://ohfax.com/index.md)
- [Overview — Oh Fax Docs](https://ohfax.com/docs): What Oh Fax is and how to send from a browser, agent, or API. (Markdown: https://ohfax.com/docs.md)
- [Quickstart — Oh Fax Docs](https://ohfax.com/docs/quickstart): Send a fax in the browser, from Account with an API key, or via MCP. (Markdown: https://ohfax.com/docs/quickstart.md)
- [API — Oh Fax Docs](https://ohfax.com/docs/api): REST quote, send, status, and receipt with API key auth and idempotency. (Markdown: https://ohfax.com/docs/api.md)
- [MCP — Oh Fax Docs](https://ohfax.com/docs/mcp): Connect Claude Code or any MCP client to Oh Fax. (Markdown: https://ohfax.com/docs/mcp.md)
- [CLI — Oh Fax Docs](https://ohfax.com/docs/cli): ohfax command-line client for quote, send, status, and receipt. (Markdown: https://ohfax.com/docs/cli.md)
- [Webhooks — Oh Fax Docs](https://ohfax.com/docs/webhooks): Signed fax.delivered and fax.failed POSTs to your endpoint. (Markdown: https://ohfax.com/docs/webhooks.md)
- [Limits — Oh Fax Docs](https://ohfax.com/docs/limits): Destinations, document limits, retention, refunds, and acceptable use. (Markdown: https://ohfax.com/docs/limits.md)
- [Pricing — Oh Fax](https://ohfax.com/pricing): $1.00 per fax by card for up to 25 pages, 2¢ a page after that. 2¢ a page from a prepaid balance or MPP stablecoin. The exact price is shown before you pay. (Markdown: https://ohfax.com/pricing.md)
- [Oh Fax compared with other fax services — Oh Fax](https://ohfax.com/compare): Prices, subscriptions, APIs and account requirements for FaxZero, WiseFax, eFax, Fax.Plus, iFax, RingCentral, Faxify and other fax services, next to Oh Fax. As of October 2026, with sources. (Markdown: https://ohfax.com/compare.md)
- [Privacy Policy — Oh Fax](https://ohfax.com/privacy): How Oh Fax collects, uses, and retains data for outbound US/CA fax. (Markdown: https://ohfax.com/privacy.md)
- [Terms of Service — Oh Fax](https://ohfax.com/terms): Terms for using Oh Fax outbound US/CA fax: payments, refunds, agents, and acceptable use. (Markdown: https://ohfax.com/terms.md)
- [Changelog — Oh Fax](https://ohfax.com/changelog): Updates to Oh Fax pricing, API, and agent discovery. (Markdown: https://ohfax.com/changelog.md)
- [Fax a court — Oh Fax](https://ohfax.com/use-cases/fax-a-court): Prepare and send a PDF to a court with Oh Fax, after confirming recipient instructions. (Markdown: https://ohfax.com/use-cases/fax-a-court.md)
- [Fax a doctor's office — Oh Fax](https://ohfax.com/use-cases/fax-a-doctors-office): Prepare and send a PDF to your doctor's office with Oh Fax, after confirming recipient instructions. (Markdown: https://ohfax.com/use-cases/fax-a-doctors-office.md)
- [Fax a pharmacy — Oh Fax](https://ohfax.com/use-cases/fax-a-pharmacy): Prepare and send a PDF to a pharmacy with Oh Fax, after confirming recipient instructions. (Markdown: https://ohfax.com/use-cases/fax-a-pharmacy.md)
- [Fax an insurance company — Oh Fax](https://ohfax.com/use-cases/fax-an-insurance-company): Prepare and send a PDF to an insurance company with Oh Fax, after confirming recipient instructions. (Markdown: https://ohfax.com/use-cases/fax-an-insurance-company.md)
- [Send a fax from ChatGPT — Oh Fax](https://ohfax.com/use-cases/fax-from-chatgpt): Connect ChatGPT to Oh Fax MCP to quote and send a PDF to the US or Canada. (Markdown: https://ohfax.com/use-cases/fax-from-chatgpt.md)
- [Send a fax from Claude — Oh Fax](https://ohfax.com/use-cases/fax-from-claude): Connect Claude to Oh Fax MCP to quote and send a PDF to the US or Canada. (Markdown: https://ohfax.com/use-cases/fax-from-claude.md)
- [Send a fax from Codex — Oh Fax](https://ohfax.com/use-cases/fax-from-codex): Connect Codex to Oh Fax MCP to quote and send a PDF to the US or Canada. (Markdown: https://ohfax.com/use-cases/fax-from-codex.md)
- [Send a fax from Cursor — Oh Fax](https://ohfax.com/use-cases/fax-from-cursor): Connect Cursor to Oh Fax MCP to quote and send a PDF to the US or Canada. (Markdown: https://ohfax.com/use-cases/fax-from-cursor.md)
- [Fax the DMV — Oh Fax](https://ohfax.com/use-cases/fax-the-dmv): Prepare and send a PDF to the DMV with Oh Fax, after confirming recipient instructions. (Markdown: https://ohfax.com/use-cases/fax-the-dmv.md)
- [Fax the IRS — Oh Fax](https://ohfax.com/use-cases/fax-the-irs): Prepare and send a PDF to the IRS with Oh Fax, after confirming recipient instructions. (Markdown: https://ohfax.com/use-cases/fax-the-irs.md)
- [Send a fax without an account — Oh Fax](https://ohfax.com/use-cases/send-a-fax-without-an-account): Send a one-off PDF fax to the US or Canada using hosted card checkout. (Markdown: https://ohfax.com/use-cases/send-a-fax-without-an-account.md)
- [Send a W-9 by fax — Oh Fax](https://ohfax.com/use-cases/send-a-w9-by-fax): Prepare and send a PDF to the W-9 requester with Oh Fax, after confirming recipient instructions. (Markdown: https://ohfax.com/use-cases/send-a-w9-by-fax.md)
- [Oh Fax vs Documo: price, account, and agent support — Oh Fax](https://ohfax.com/vs/documo): An honest comparison of Oh Fax and Documo for sending a fax in the US or Canada, with prices checked Oct 24, 2026 on Documo's own site. (Markdown: https://ohfax.com/vs/documo.md)
- [Oh Fax vs Dropbox Fax: price, account, and agent support — Oh Fax](https://ohfax.com/vs/dropbox-fax): An honest comparison of Oh Fax and Dropbox Fax for sending a fax in the US or Canada, with prices checked Oct 24, 2026 on Dropbox Fax's own site. (Markdown: https://ohfax.com/vs/dropbox-fax.md)
- [Oh Fax vs eFax: price, account, and agent support — Oh Fax](https://ohfax.com/vs/efax): An honest comparison of Oh Fax and eFax for sending a fax in the US or Canada, with prices checked Oct 24, 2026 on eFax's own site. (Markdown: https://ohfax.com/vs/efax.md)
- [Oh Fax vs Fax.Plus: price, account, and agent support — Oh Fax](https://ohfax.com/vs/fax-plus): An honest comparison of Oh Fax and Fax.Plus for sending a fax in the US or Canada, with prices checked Oct 24, 2026 on Fax.Plus's own site. (Markdown: https://ohfax.com/vs/fax-plus.md)
- [Oh Fax vs Faxify: price, account, and agent support — Oh Fax](https://ohfax.com/vs/faxify): An honest comparison of Oh Fax and Faxify for sending a fax in the US or Canada, with prices checked Oct 24, 2026 on Faxify's own site. (Markdown: https://ohfax.com/vs/faxify.md)
- [Oh Fax vs FaxZero: price, account, and agent support — Oh Fax](https://ohfax.com/vs/faxzero): An honest comparison of Oh Fax and FaxZero for sending a fax in the US or Canada, with prices checked Oct 24, 2026 on FaxZero's own site. (Markdown: https://ohfax.com/vs/faxzero.md)
- [Oh Fax vs iFax: price, account, and agent support — Oh Fax](https://ohfax.com/vs/ifax): An honest comparison of Oh Fax and iFax for sending a fax in the US or Canada, with prices checked Oct 24, 2026 on iFax's own site. (Markdown: https://ohfax.com/vs/ifax.md)
- [Oh Fax vs mFax: price, account, and agent support — Oh Fax](https://ohfax.com/vs/mfax): An honest comparison of Oh Fax and mFax for sending a fax in the US or Canada, with prices checked Oct 24, 2026 on mFax's own site. (Markdown: https://ohfax.com/vs/mfax.md)
- [Oh Fax vs Phaxio (Sinch): price, account, and agent support — Oh Fax](https://ohfax.com/vs/phaxio): An honest comparison of Oh Fax and Phaxio (Sinch) for sending a fax in the US or Canada, with prices checked Oct 24, 2026 on Phaxio (Sinch)'s own site. (Markdown: https://ohfax.com/vs/phaxio.md)
- [Oh Fax vs RingCentral Fax: price, account, and agent support — Oh Fax](https://ohfax.com/vs/ringcentral): An honest comparison of Oh Fax and RingCentral Fax for sending a fax in the US or Canada, with prices checked Oct 24, 2026 on RingCentral Fax's own site. (Markdown: https://ohfax.com/vs/ringcentral.md)
- [Oh Fax vs WiseFax: price, account, and agent support — Oh Fax](https://ohfax.com/vs/wisefax): An honest comparison of Oh Fax and WiseFax for sending a fax in the US or Canada, with prices checked Oct 24, 2026 on WiseFax's own site. (Markdown: https://ohfax.com/vs/wisefax.md)
- [Fax comparisons — Oh Fax](https://ohfax.com/vs/): Compare Oh Fax with other fax options. (Markdown: https://ohfax.com/vs/index.md)
- [Fax use cases — Oh Fax](https://ohfax.com/use-cases/): Guides to sending a fax with Oh Fax. (Markdown: https://ohfax.com/use-cases/index.md)

Full page content: https://ohfax.com/llms-full.txt