Braintrust is a observability & evals option for building AI agents. Eval-first platform — scorers, datasets and a playground for prompt iteration.
BRAINTRUST_API_KEY=
| Option | What it does | Licence | Self-host |
|---|---|---|---|
| Braintrust | Eval-first platform — scorers, datasets and a playground for prompt iteration. | Proprietary | Yes |
| Langfuse | Open-source tracing, prompt management and evals. Self-hostable in one compose file. | Open source | Yes |
| LangSmith | Tracing, datasets and evals from the LangChain team. | Proprietary | No |
| Arize Phoenix | OpenTelemetry-native tracing and evals you can run locally. | Open source | Yes |
| Pydantic Logfire | OpenTelemetry observability with first-class Python and Pydantic AI support. | Open source | No |
| promptfoo | Local eval and red-team harness that runs in CI. No account needed. | Open source | Yes |
Every page here answers to Accept: text/markdown and returns the same content at roughly a tenth the tokens. No separate site, no toggle — same URL.
curl -s -H "Accept: text/markdown" https://newagent.build/c/braintrust