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Some operations consume credits, the unit Brew meters AI generation and media rendering with. Each credit is worth $0.01 of underlying spend. Every credit-metered operation charges only on success. There are two metering modes:
  • Usage-metered: email generation, email import, AI email edits, semantic brand-image search, and image generation charge the actual model usage (token input/output for the email agent; embedding/image-gateway cost for search + image generation). The cost scales with the work, so there is no fixed number and no X-Credit-Cost header. The call still gates: an empty balance is rejected up front.
  • Fixed: every other media/render operation charges a flat, published per-operation cost, reported via the X-Credit-Cost response header.

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Which operations cost credits

OperationRouteMetering
Generate an emailPOST /v1/emailsUsage (tokens)
Import an email (HTML / MJML / JSX → editable design)POST /v1/emails/importUsage (tokens)
Edit an email (AI prompt edit)PATCH /v1/emails/{emailId}Usage (tokens)
Semantic brand-image searchGET /v1/brand/images?q=…Usage (embedding)
Generate an imagePOST /v1/content/generate-imageUsage (image)
Preview an email across real inboxes/devicesPOST /v1/emails/{emailId}/client-previewsFixed
Audit an email’s accessibility (WCAG 2.1)POST /v1/emails/{emailId}/accessibility-auditFixed
Validate contact deliverabilityPOST /v1/contacts/validateFixed (per address)
Validate on ingestion (opt-in)POST /v1/contacts / POST /v1/contacts/import-csv with validate: trueFixed (per address)
Generate / animate a GIFPOST /v1/content/gif (from: "prompt" | "image" | "video")Fixed
Optimize / resize an imagePOST /v1/content/transform (operation: "optimize" | "resize")Fixed
Render HTML to a PNGPOST /v1/content/html-to-pngFixed
Add an image (saves to the brand image library)POST /v1/content/add-imageFixed
Everything else is free: all reads (including the no-q browse of GET /v1/brand/images).
Contact validation is metered per address, the X-Credit-Cost for a call is the per-address cost times the number of addresses you submit (e.g. validating 100 addresses charges 100× the unit cost). See GET /v1/help → credits.operations for the current per-address unit. The same per-address rate applies to the opt-in validate: true flag on POST /v1/contacts and POST /v1/contacts/import-csv; batches over 100 addresses upsert first and validate as a background job that meters per address as it runs.
For fixed operations the cost is published and does not vary with output size, the authoritative number for a call is its X-Credit-Cost response header. For usage-metered operations the charge equals the real token/image cost the work incurred (no header). The full per-operation metering table is available machine-readably at GET /v1/help → credits.operations.
These fixed-cost calls are value-aligned. You are never charged for an empty result. The client-preview render bills only when at least one client actually produces a screenshot; the accessibility audit bills only when it completes; contact validation bills only when at least one address is checked. If nothing is produced (nothing finished in time, or the service is temporarily unavailable) the call returns a retryable 503 SERVICE_UNAVAILABLE and is not billed.

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Check your balance: GET /v1/usage

There is no dry-run cost preview. Credit-metered calls just charge on success; if you want to know what you can afford before you call, read your balance from the billing surface: 
curl "https://brew.new/api/v1/usage" \
  -H "Authorization: Bearer brew_…"

{
  "plan": "pro",
  "credits":    { "limit": 500, "used": 260, "remaining": 240 },
  "emailSends": { "limit": 50000, "used": 1200, "remaining": 48800 },
  "period":     { "start": "2026-06-01T00:00:00.000Z", "end": "2026-07-01T00:00:00.000Z" }
}
A null limit / remaining means unlimited. credits is the AI/media balance; emailSends is your monthly delivery allowance. Both reset at the period.end boundary. GET /v1/usage requires the emails scope.

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What a real (charged) call reports

A successful fixed-cost call charges the published cost exactly once and returns two headers:
HeaderMeaning
X-Credit-CostCredits charged for this call.
X-Credits-RemainingBalance after the charge.
Usage-metered calls (email generate/edit, image generation) bill the actual model usage to your account and do not return these headers. Read your balance from GET /v1/usage before and after to see the delta. Charging is idempotent: a retry with the same Idempotency-Key replays the original response and is not charged again.

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Errors

CodeStatusWhen
INSUFFICIENT_CREDITS402Your balance is too low: below the fixed cost (fixed ops) or empty (usage-metered ops). details carries { cost, remaining, planKey }. Top up / upgrade. There’s no Retry-After because credits reset at the billing-period boundary (read it from GET /v1/usage’s period.end).
SERVICE_UNAVAILABLE503The credit balance could not be verified (a transient billing-backend outage). The gate fails closed. It refuses rather than do paid work it can’t meter. Retryable: a Retry-After header tells you when.
402 is a confirmed empty balance; 503 is “can’t check right now, try again shortly”. Branch on the code, never on the message.

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