Documentation

Send faxes with agent-safe defaults.

AgentFax exposes a stable JSON API for fax delivery. Live Telnyx sending currently accepts `media_url` or `media_name`; sandbox mode also accepts generated text and HTML for validation workflows.

Authentication

Use bearer API keys. Production keys are returned once and stored hashed.

Authorization: Bearer afx_live_...

Send a Fax

POST /v1/faxes
Content-Type: application/json
Idempotency-Key: invoice-123-v1

{
  "to": "+13125550123",
  "media_url": "https://example.com/invoice-123.pdf",
  "client_reference": "invoice-123",
  "dry_run": false
}

Idempotency

Pass `Idempotency-Key` on every send attempt. If the same account repeats the same key, AgentFax returns the original fax record instead of transmitting a second fax.

Webhooks

Provider delivery events are normalized into AgentFax events. Register account-level webhook endpoints with `POST /v1/webhooks`, or pass a one-off `webhook_url` on an individual fax.

{
  "type": "fax.delivered",
  "fax_id": "fax_...",
  "status": "delivered",
  "created_at": "2026-07-03T14:30:00.000Z"
}

Deliveries include `AgentFax-Event-Id`, `AgentFax-Timestamp`, and `AgentFax-Signature` headers. Verify the signature with the signing secret returned when the webhook endpoint is created.

If a send request includes a one-off `webhook_url`, the fax response includes `webhook_signing_secret` for that per-fax callback path.

OpenAPI and LLM Docs

The Worker serves `/openapi.json`, `/llms.txt`, and `/llms-full.txt` so agents can discover the API without scraping a marketing page.

Billing

`POST /billing/onboarding` creates a pending account and subscription Checkout URL. After the customer returns with `session_id`, call `POST /billing/claim` once with the one-time `claim_token` returned by onboarding. The claim verifies Checkout and returns the first API key. Authenticated accounts can call `POST /billing/portal` after Stripe customer linkage to manage payment methods and subscription state.

POST /billing/onboarding
{
  "name": "Acme Ops",
  "email": "ops@example.com"
}

POST /billing/claim
{
  "checkout_session_id": "cs_live_...",
  "claim_token": "afx_claim_..."
}