Credits & Rate Limits

TuneLab bills by credits, not request count. Cache hits are free. You only pay when we actually do DSP work. Every response tells you exactly what you were charged via the _meta.credits_used field.

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Cache hits are always free.
If we have the track pre-computed (9.3M+ tracks), you pay zero credits. Only misses trigger compute.

Credit weights

Operation	Credits	Notes
Cache lookup (any endpoint)	0	Always free
`GET /v1/resolve/{id}`	0	Identity only, always free
`GET /v1/key-bpm` (miss)	2	On-demand compute
`GET /v1/analyze` (miss)	10	Full features including mood
`POST /v1/bpm` (upload)	2	Always charged
`POST /v1/key` (upload)	2	Always charged
`POST /v1/analyze/upload`	10	Async, returns 202
`POST /v1/structure`	10	Song structure segmentation
`POST /v1/separate`	6 × minutes	2-stem (vocal/instrumental)
`POST /v1/separate?stems=4`	10 × minutes	4-stem (drums/bass/vocal/other)
`POST /v1/transcribe`	10 × minutes	Audio-to-MIDI
`POST /v1/master`	5 × minutes	Auto-mastering

Plan tiers

Plan	Price	Credits / month	Concurrency
Free	$0	100 (one-time)	1 req/s
Starter	$29	3,000	3
Pro	$99	12,000	10
Scale	$499	75,000	25
Enterprise	$2,500+	Custom	Custom

Rate limit headers

Every response includes:

X-Credits-Remaining — current balance after this request
X-RateLimit-Limit — requests allowed in current window
X-RateLimit-Remaining — requests left in current window
X-RateLimit-Reset — Unix timestamp when the window resets

When credits run out

The API returns 402 Payment Required and the response body includes error: "insufficient_credits". Top up via credit packs in the dashboard or wait for your monthly refresh.

No surprise billing.
We never auto-charge for overage. If you hit 0 credits, you get 402s until you top up. Your card is never charged beyond your plan.