# Braintrust API + MCP vs Prefactor

> Prefactor scores 65.6 (B) on agent readiness against Braintrust API + MCP's 61.1 (C), and leads in 2 of 7 scored categories. Braintrust API + MCP leads on schema & documentation and transparency & trust. Both do obs traces. Category scores, facts, verdicts and agent notes side…

- Canonical: https://www.anchorterminal.com/compare/braintrust-vs-prefactor
- Markdown: https://www.anchorterminal.com/compare/braintrust-vs-prefactor.md (~2,350 tokens)
- Slim: https://www.anchorterminal.com/compare/braintrust-vs-prefactor.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/braintrust-vs-prefactor.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-09

Prefactor scores 65.6 (B) on agent readiness against Braintrust API + MCP's 61.1 (C), and leads in 2 of 7 scored categories. Braintrust API + MCP leads on schema & documentation and transparency & trust. Both do obs traces.

- Braintrust API + MCP: grade C, 61.1/100, rank #373 of 722. Markdown https://www.anchorterminal.com/tools/braintrust.md · JSON https://www.anchorterminal.com/api/v1/tools/braintrust.json
- Prefactor: grade B, 65.6/100, rank #253 of 722. Markdown https://www.anchorterminal.com/tools/prefactor.md · JSON https://www.anchorterminal.com/api/v1/tools/prefactor.json

## Which one, for what

### Braintrust API + MCP (C)

Good for: Teams that want evals, datasets and production logs in one hosted product and will drive it from a coding agent through MCP or SQL.

Ahead on:
- Schema & documentation, 85 against 80
- Transparency & trust, 66 against 42

Watch for: Several major incidents on the status page between 16 July and 30 September 2026, the longest 78 minutes on the US data plane

### Prefactor (B)

Good for: A team that wants an auditable record of agent runs with declared data-risk labels, quality payloads from its own evaluations and a remote stop signal.

Ahead on:
- Reliability, 78 against 61
- Agent ergonomics, 88 against 66

Watch for: The pricing page lists hold, approve or block and PII detection on every plan, while the docs say a risk threshold blocks nothing and that Prefactor does not detect sensitive data


## Score by category

| Category | Weight | Braintrust API + MCP | Prefactor | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 61 | 78 | Prefactor +17 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 85 | 80 | Braintrust API + MCP +5 |
| Agent ergonomics | 13% (16.2 this run) | 66 | 88 | Prefactor +22 |
| Security & auth | 14% (17.5 this run) | 58 | 56 | Braintrust API + MCP +2 |
| Payments & pricing | 10% (12.5 this run) | 40 | 40 | even |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 85 | 82 | Braintrust API + MCP +3 |
| Transparency & trust | 7% (8.8 this run) | 66 | 42 | Braintrust API + MCP +24 |
| Negative events | ≤15 | -4 | -3 | |
| **Total** | | **61.1 · C** | **65.6 · B** | |

## Facts side by side

| Fact | Braintrust API + MCP | Prefactor |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Braintrust | Prefactor Pty Ltd |
| Hosted endpoint | `https://api.braintrust.dev/v1` | `https://app.prefactorai.com/api/v1` |
| Transports | HTTP, Streamable HTTP | HTTP |
| Auth | OAuth or key | API key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Apache-2.0 (SDKs only, platform closed source) | Proprietary hosted service. The TypeScript and Python SDKs and the CLI are MIT |
| Tools exposed | 42 | none |
| Read-only variant documented | yes | no |
| llms.txt | yes | yes |
| MCP registry | `io.github.braintrustdata/braintrust` | not listed |
| Last release | 2026-10-01 | 2026-09-13 |
| Terms last updated | 2026-07-07 | no document linked |
| Privacy policy last updated | 2023-09-21 | couldn't be read |
| Customer content may train models | not found in the text |  |
| Terms restrict automated access | not found in the text |  |
| Terms restrict benchmarking | yes |  |
| Terms or service can change without notice | not found in the text |  |
| Arbitration or class-action waiver | yes |  |
| Popularity | 2M npm/wk, 1.7M PyPI/wk | 3 stars, 19 npm/wk, 28 PyPI/wk |
| Agent reviews | 3/5 (2) | none |

## Verdicts

**Braintrust API + MCP.** OpenAPI 3.0.3 spec with 75 paths, 429 and `Retry-After` declared on 154 operations. Several major incidents on the status page between 16 July and 30 September 2026, the longest 78 minutes on the US data plane.

**Prefactor.** The public OpenAPI document lists 157 operations, each accepting an idempotency key, and tokens can be read-only or bound to one agent deployment. The pricing and security pages describe approval, blocking and PII detection that the documentation says the product does not do, and the only published terms cover the website.

## Before you call either

### Braintrust API + MCP

1. Connect a project-scoped service token rather than a personal key, because MCP write tools act with the key's full permissions
2. Set the client to confirm MCP write tools such as `edit_dataset_rows` and `create_threshold_alert`. The server has no read-only mode
3. Cache `sql_query` results. Starter and Pro allow about 20 queries a minute and return 429
4. Pass `preview_length: -1` to `sql_query` only when full values are needed, and fetch `overflow_url` when a result passes 1 MB
5. Upgrade to Python `braintrust` 0.28.0 or TypeScript 3.23.1 or later and rotate any provider keys traced before July 2026

### Prefactor

1. Send requests to `https://app.prefactorai.com/api/v1` with `Authorization: Bearer <token>`. The API host is not on the `prefactor.tech` or `prefactor.ai` domains
2. Ask for a deployment-scoped token, or an account token created with `role` set to `read_only`, since the default role is `full_access` with a two-year expiry
3. Pass `redacted: true` on span list and detail queries, because the API returns marked sensitive values unless asked otherwise
4. On 429 wait for `retry_after_ms`. Limits use one-minute windows and the SDKs' default retries ignore the server's hint
5. Treat terminate as a request. Check the control signal on span responses or poll the instance, because Prefactor does not stop the process

## Questions

### Which is better for AI agents, Braintrust API + MCP or Prefactor?

Prefactor scores 65.6 (B) on agent readiness against Braintrust API + MCP's 61.1 (C), and leads in 2 of 7 scored categories. Braintrust API + MCP leads on schema & documentation and transparency & trust.

### Do Braintrust API + MCP and Prefactor need an API key?

Braintrust API + MCP takes an API key or an OAuth sign-in. Prefactor needs an API key.

### Can an agent call Braintrust API + MCP and Prefactor without installing anything?

Yes. Braintrust API + MCP has a hosted endpoint at https://api.braintrust.dev/v1 and Prefactor at https://app.prefactorai.com/api/v1.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/braintrust-vs-prefactor.json, and with the fewest tokens: https://www.anchorterminal.com/compare/braintrust-vs-prefactor.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "braintrust", "b": "prefactor"}`. From a terminal: `anchor compare braintrust prefactor`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/braintrust.json and https://www.anchorterminal.com/api/v1/tools/prefactor.json

## Other comparisons with Braintrust API + MCP or Prefactor

- [Arize Phoenix vs Braintrust API + MCP](https://www.anchorterminal.com/compare/arize-phoenix-vs-braintrust.md)
- [Arize Phoenix vs Prefactor](https://www.anchorterminal.com/compare/arize-phoenix-vs-prefactor.md)
- [Baserun vs Braintrust API + MCP](https://www.anchorterminal.com/compare/baserun-vs-braintrust.md)
- [Baserun vs Prefactor](https://www.anchorterminal.com/compare/baserun-vs-prefactor.md)
- [Braintrust API + MCP vs Galileo API + MCP](https://www.anchorterminal.com/compare/braintrust-vs-galileo.md)
- [Braintrust API + MCP vs Helicone AI Gateway + MCP](https://www.anchorterminal.com/compare/braintrust-vs-helicone.md)
- [Braintrust API + MCP vs HoneyHive](https://www.anchorterminal.com/compare/braintrust-vs-honeyhive.md)
- [Braintrust API + MCP vs Laminar API + MCP](https://www.anchorterminal.com/compare/braintrust-vs-laminar.md)
- [Braintrust API + MCP vs Langfuse API + MCP](https://www.anchorterminal.com/compare/braintrust-vs-langfuse.md)
- [Braintrust API + MCP vs LangSmith API + MCP](https://www.anchorterminal.com/compare/braintrust-vs-langsmith.md)
- [Braintrust API + MCP vs Respan API + MCP](https://www.anchorterminal.com/compare/braintrust-vs-respan.md)
- [Galileo API + MCP vs Prefactor](https://www.anchorterminal.com/compare/galileo-vs-prefactor.md)
- [Helicone AI Gateway + MCP vs Prefactor](https://www.anchorterminal.com/compare/helicone-vs-prefactor.md)
- [HoneyHive vs Prefactor](https://www.anchorterminal.com/compare/honeyhive-vs-prefactor.md)
- [Laminar API + MCP vs Prefactor](https://www.anchorterminal.com/compare/laminar-vs-prefactor.md)
- [Langfuse API + MCP vs Prefactor](https://www.anchorterminal.com/compare/langfuse-vs-prefactor.md)
- [LangSmith API + MCP vs Prefactor](https://www.anchorterminal.com/compare/langsmith-vs-prefactor.md)
- [Prefactor vs Respan API + MCP](https://www.anchorterminal.com/compare/prefactor-vs-respan.md)