# Braintrust API + MCP vs LangWatch

> LangWatch scores 65.5 (B) on agent readiness against Braintrust API + MCP's 61.1 (C), and leads in 5 of 7 scored categories. Braintrust API + MCP leads on reliability. Both do obs traces. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/braintrust-vs-langwatch
- Markdown: https://www.anchorterminal.com/compare/braintrust-vs-langwatch.md (~2,500 tokens)
- Slim: https://www.anchorterminal.com/compare/braintrust-vs-langwatch.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/braintrust-vs-langwatch.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

LangWatch scores 65.5 (B) on agent readiness against Braintrust API + MCP's 61.1 (C), and leads in 5 of 7 scored categories. Braintrust API + MCP leads on reliability. Both do obs traces.

- Braintrust API + MCP: grade C, 61.1/100, rank #433 of 842. Markdown https://www.anchorterminal.com/tools/braintrust.md · JSON https://www.anchorterminal.com/api/v1/tools/braintrust.json
- LangWatch: grade B, 65.5/100, rank #291 of 842. Markdown https://www.anchorterminal.com/tools/langwatch.md · JSON https://www.anchorterminal.com/api/v1/tools/langwatch.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:
- Reliability, 61 against 53

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

### LangWatch (B)

Good for: Teams that want tracing, evaluations and simulated-user agent tests in one open-source product, hosted in the EU or self-hosted, and that drive it from a coding assistant through MCP or the CLI.

Ahead on:
- Security & auth, 71 against 58
- Maintenance & community, 90 against 85
- Transparency & trust, 75 against 66

Also in its favour:
- Runs on your own machine
- Open source

Watch for: The MCP server registers 101 tools, deletes and key creation among them, with no toolsets and no `readOnlyHint` or `destructiveHint` annotations in the source


## Score by category

| Category | Weight | Braintrust API + MCP | LangWatch | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 61 | 53 | Braintrust API + MCP +8 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 85 | 87 | LangWatch +2 |
| Agent ergonomics | 13% (16.2 this run) | 66 | 67 | LangWatch +1 |
| Security & auth | 14% (17.5 this run) | 58 | 71 | LangWatch +13 |
| 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 | 90 | LangWatch +5 |
| Transparency & trust | 7% (8.8 this run) | 66 | 75 | LangWatch +9 |
| Negative events | ≤15 | -4 | -2 | |
| **Total** | | **61.1 · C** | **65.5 · B** | |

## Facts side by side

| Fact | Braintrust API + MCP | LangWatch |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Braintrust | Reasoning Engine B.V. (LangWatch) |
| Hosted endpoint | `https://api.braintrust.dev/v1` | `https://app.langwatch.ai` |
| Transports | HTTP, Streamable HTTP | HTTP, Streamable HTTP, SSE (legacy), stdio |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Apache-2.0 (SDKs only, platform closed source) | Apache 2.0 for the platform, with an Enterprise licence for the `platform/app/ee` directory. The SDKs and the MCP server are MIT |
| Tools exposed | 42 | 101 |
| Read-only variant documented | yes | no |
| llms.txt | yes | yes |
| MCP registry | `io.github.braintrustdata/braintrust` | not listed |
| Last release | 2026-10-01 | 2026-10-02 |
| Terms last updated | 2026-07-07 | 2026-09-22 |
| Privacy policy last updated | 2023-09-21 | 2026-09-29 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | yes |
| Terms restrict benchmarking | yes | not found in the text |
| Terms or service can change without notice | not found in the text | yes |
| Arbitration or class-action waiver | yes | not found in the text |
| Popularity | 2M npm/wk, 1.7M PyPI/wk | 4.9k stars, 50k npm/wk, 87k 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.

**LangWatch.** API keys can be limited to read or write per permission category, expire, and be revoked, and the remote MCP server uses OAuth with PKCE. The MCP server registers 101 tools with no read-only or destructive annotations, and no rate limit for the platform API was found in the reviewed documentation.

## 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

### LangWatch

1. Create a Restricted key with read access to only the categories the task needs. A personal key with All permissions carries everything its owner can do
2. Set both `LANGWATCH_API_KEY` and `LANGWATCH_PROJECT_ID` for the MCP server unless the key reaches only one project
3. Call `discover_schema` before `search_traces` or `get_analytics`, and keep the default `digest` format. `json` returns the full raw trace
4. Allowlist MCP tools in the client. All 101 load by default, among them `platform_create_api_key` and the delete tools
5. Follow `next_cursor` until it is null on list endpoints. A full page does not mean more rows exist

## Questions

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

LangWatch scores 65.5 (B) on agent readiness against Braintrust API + MCP's 61.1 (C), and leads in 5 of 7 scored categories. Braintrust API + MCP leads on reliability.

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

Both take an API key or an OAuth sign-in.

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

Yes. Braintrust API + MCP has a hosted endpoint at https://api.braintrust.dev/v1 and LangWatch at https://app.langwatch.ai.

### Are Braintrust API + MCP and LangWatch open source?

No open-source release is listed for Braintrust API + MCP. LangWatch is open source (Apache 2.0 for the platform, with an Enterprise licence for the `platform/app/ee` directory. The SDKs and the MCP server are MIT).


## For agents

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

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