fal video models vs Runway API

fal video models

One key and one queue API reach 137 active text-to-video endpoints, each with a published price, an OpenAPI document and an llms.txt. Billing units, duration formats and audio pricing differ per model, there is no free tier, and a person must sign up in a browser and buy credit.

Runway API

OpenAPI 3.1, llms.txt and Markdown copies of every docs page. Gen-3 Alpha Turbo and Gen-4 Aleph were removed on 2026-07-30 with no prior notice in the changelog.

fal video models

1. Submit to queue.fal.run, keep the request_id, then poll status_url or set fal_webhook. Never resubmit to check progress, because each submit is a new billable job
2. Read https://fal.ai/models/<endpoint-id>/llms.txt before a call. duration is the string "5" on Kling, "8s" on Veo 3.1 and an integer on Wan 3.0
3. Set generate_audio on purpose. It defaults to true and raises the Kling v3 Pro price from $0.112 to $0.168 a second and Veo 3.1 from $0.20 to $0.40
4. Check metadata.status in https://api.fal.ai/v1/models before pinning an endpoint. Deprecated endpoints carry no removal date
5. Use an API-scope key, never an ADMIN key. A new account runs 2 requests at once, so long video jobs queue behind each other
6. The MCP relay has no server-side approval gate. Call get_pricing and get the owner's approval before submit_job

Runway API

1. Send X-Runway-Version: 2024-11-06 on every request or it fails
2. Use the SDK's wait-for-output helper or poll GET /v1/tasks/{id} until SUCCEEDED or FAILED
3. Don't retry a SAFETY.* failure unchanged. It's moderation, not an outage
4. Take model IDs from the models page, not memory. Two were removed without notice on 2026-07-30
5. Copy outputs to your own storage. URLs expire within 24 to 48 hours