# Sinch API Fax Send

> Send a fax via Sinch Fax API

- Skill: `sinch/sinch-api-fax-send` (Agent Skill)
- Install (CLI): `npx skillmds@latest add sinch/sinch-api-fax-send`
- Raw SKILL.md: https://api.skillmd.com/api/skills/sinch/sinch-api-fax-send/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: sinch (https://skillmd.com/u/sinch)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/sinch/sinch-api-fax-send

---


# Send Fax

Send a fax to a recipient using the Sinch Fax API. Document must be available at a public URL (PDF or other supported format). Uses OAuth2 (project key id/secret).

**IMPORTANT: Execute this command directly. Do NOT generate script files. Perform the API call immediately.**

## Input

- `--to` / `-t`: Recipient fax number (E.164 or national format) - required
- `--content-url` / `-u`: Public URL of the document to fax (e.g. PDF) - required
- `--callback-url` / `-c`: Optional webhook URL for status callbacks

Arguments: $ARGUMENTS

## Instructions

**Execute these steps directly - do not write code or scripts:**

0. If $ARGUMENTS empty: ask for recipient fax number and document URL. Otherwise parse.

1. Validate: --to (non-empty), --content-url (valid HTTPS URL). Get CONVERSATION_PROJECT_ID, CONVERSATION_KEY_ID, CONVERSATION_KEY_SECRET (or FAX_* equivalents). Fax API uses OAuth2. Base: https://fax.api.sinch.com/v3. If missing, report "Sinch API is not configured."

2. Request body: to, contentUrl; optional callbackUrl. POST https://fax.api.sinch.com/v3/projects/{projectId}/faxes with OAuth2 Bearer token.

3. On success: "✅ Fax sent" with fax ID. Handle 400, 401, 404 with clear messages.

4. Handle all errors gracefully.

## Examples

```
/sinch-api-fax-send --to=+14155551234 --content-url=https://example.com/document.pdf
/sinch-api-fax-send -t +14155551234 -u https://example.com/doc.pdf
```

## API Reference

- **Base URL**: https://fax.api.sinch.com/v3
- **Endpoint**: POST /projects/{projectId}/faxes
- **Documentation**: https://developers.sinch.com/docs/fax/