Is there a free LLM eval or observability API?

Yes. As of 2026-09-29, 3 free LLM eval and observability offers we track are available, each dated when last verified against the provider's page.

OfferProviderStatusWhat it offersExpiryVerifiedSourceCaveats
Braintrust Starter planBraintrustavailable$10 model credits/month, 1 GB processed data/month, 10K scores/month, 14-day data retention, unlimited users, projects, datasets, playgrounds and experiments; no credit cardno stated expiry2026-09-16source14-day retention. Re-read first-party 2026-09-16 and holds. ADDED: the Starter plan carries 14-day data retention, which this row did not state — an evaluation history older than a fortnight is gone, which matters m…
Langfuse Cloud Hobby planLangfuseavailable50,000 units/month, 30-day data access, 2 users, all platform features with limitsno stated expiry2026-09-16sourceOSS self-host is unlimited and free as an alternative
LangSmith Developer planLangChainavailable5,000 base traces/month (14-day retention), 1 seat, core tracing + evalsno stated expiry2026-09-16sourcesingle seat; pay-as-you-go beyond 5K traces

Free LLM APIs, no card · Free AI APIs an agent can sign up for · Machine-readable: ai-deals.json