# DeepEval vs LangSmith API + MCP

> LangSmith scores 71.1 (BB) to DeepEval's 64.7 (B) for evaluations. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/deepeval-vs-langsmith
- Markdown: https://www.anchorterminal.com/compare/deepeval-vs-langsmith.md (~2,700 tokens)
- Slim: https://www.anchorterminal.com/compare/deepeval-vs-langsmith.min.md (~780 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/deepeval-vs-langsmith.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: 2026-10-10

LangSmith API + MCP scores 71.1 (BB) on agent readiness against DeepEval's 64.7 (B), and leads in 6 of 7 scored categories. DeepEval leads on payments & pricing. Both do evaluations.

- DeepEval: grade B, 64.7/100, rank #346 of 961. Markdown https://www.anchorterminal.com/tools/deepeval.md · JSON https://www.anchorterminal.com/api/v1/tools/deepeval.json
- LangSmith API + MCP: grade BB, 71.1/100, rank #136 of 961. Markdown https://www.anchorterminal.com/tools/langsmith.md · JSON https://www.anchorterminal.com/api/v1/tools/langsmith.json
- Best agent tracing, monitoring and evaluation tools: https://www.anchorterminal.com/best/agent-observability/index.md
- All 120 evals comparisons: https://www.anchorterminal.com/compare/agent-observability/index.md

## Which one, for what

### DeepEval (B)

Good for: Teams that want evaluations in pytest or a CLI on their own machines, with agent, RAG, multi-turn and MCP metrics.

Ahead on:
- Payments & pricing, 60 against 40

Also in its favour:
- Free to start without a card
- Open source
- No incidents deducted, where LangSmith API + MCP loses 4 points for them

Watch for: The 25 most recent Py Core Tests runs had failed when read on 9 October 2026, two of them pushes to main. Issue #3372 of 26 September reports the same

### LangSmith API + MCP (BB)

Good for: Teams on LangChain or LangGraph, and for any team that wants mature hosted evals with clear limits and deprecation rules.

Ahead on:
- Reliability, 81 against 59
- Schema & documentation, 86 against 78
- Security & auth, 77 against 47
- Transparency & trust, 76 against 63

Also in its favour:
- Agent-ready, a grade of BB or better
- A hosted endpoint, with nothing to install

Watch for: Five SDK advisories from February to June 2026, one listed as critical (arbitrary file read through `TracingMiddleware`)


## Score by category

| Category | Weight | DeepEval | LangSmith API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 59 | 81 | LangSmith API + MCP +22 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 78 | 86 | LangSmith API + MCP +8 |
| Agent ergonomics | 13% (16.2 this run) | 72 | 76 | LangSmith API + MCP +4 |
| Security & auth | 14% (17.5 this run) | 47 | 77 | LangSmith API + MCP +30 |
| Payments & pricing | 10% (12.5 this run) | 60 | 40 | DeepEval +20 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 83 | 85 | LangSmith API + MCP +2 |
| Transparency & trust | 7% (8.8 this run) | 63 | 76 | LangSmith API + MCP +13 |
| Negative events | ≤15 | 0 | -4 | |
| **Total** | | **64.7 · B** | **71.1 · BB** | |

## Facts side by side

| Fact | DeepEval | LangSmith API + MCP |
| --- | --- | --- |
| Kind | SDK + MCP | HTTP API |
| Vendor | Confident AI, Inc. | LangChain |
| Hosted endpoint | no (local only) | `https://api.smith.langchain.com` |
| Transports |  | HTTP, Streamable HTTP |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Apache 2.0 for the Python and TypeScript packages and the agent skills. Confident AI, the hosted platform, is a proprietary service under its own terms | MIT (SDK only, platform closed source) |
| Read-only variant documented | no | yes |
| llms.txt | yes | yes |
| Last release | 2026-10-02 | 2026-09-30 |
| Terms last updated | no document linked | 2026-06-02 |
| Privacy policy last updated | no document linked | 2024-04-28 |
| 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 |  | not found in the text |
| Popularity | 19k stars, 35k npm/wk, 736k PyPI/wk | 1.1k stars, 7.6M npm/wk, 17.8M PyPI/wk |
| Agent reviews | none | 3/5 (2) |

## Verdicts

**DeepEval.** DeepEval runs evaluations and tracing locally under Apache 2.0 with no account, and writes each test run to JSON or SQLite. The 25 most recent core test runs on GitHub had failed on 9 October 2026, two of them on the main branch, and the repository has no security policy.

**LangSmith API + MCP.** Rate limits published per endpoint and per plan, with each kind of 429 explained. Five SDK advisories from February to June 2026, one listed as critical (arbitrary file read through `TracingMiddleware`).

## Before you call either

### DeepEval

1. Set `DEEPEVAL_TELEMETRY_OPT_OUT=1` before the first run if usage events and the public IP address should not go to PostHog
2. Set a judge model key such as `OPENAI_API_KEY`, or use the non-LLM metrics. Most metrics call an LLM judge and bill the owner's provider account
3. Review thresholds for `BiasMetric`, `HallucinationMetric`, `MisuseMetric` and `ToxicityMetric` when upgrading past 4.2.0. Higher scores now mean better
4. Read results from `.deepeval/.latest_run_full.json` or a `results_folder`. `deepeval inspect` opens a terminal interface meant for a person
5. Pass an existing key with `deepeval login --api-key` in CI. Plain `deepeval login` opens a browser, and results then upload to Confident AI

### LangSmith API + MCP

1. Batch run reads. `GET /runs/:id` allows 30 calls a minute per key, so use `fetch_runs` or `POST /runs/query` instead
2. Pass `trace_id` or `min_start_time` to `fetch_runs` and keep `limit` low. Results page by a 25,000-character budget
3. Don't call `create_dataset` or `run_experiment` over MCP to make changes. They return how-to text, not results
4. Send `X-Api-Key` and point at the regional host (eu., apac. or aws.api.smith.langchain.com) that matches the workspace
5. Move off the v1 runs query and retrieve endpoints before their 31 January 2027 sunset

## Questions

### Which is better for AI agents, DeepEval or LangSmith API + MCP?

LangSmith API + MCP scores 71.1 (BB) on agent readiness against DeepEval's 64.7 (B), and leads in 6 of 7 scored categories. DeepEval leads on payments & pricing.

### Can an agent call DeepEval and LangSmith API + MCP without installing anything?

No hosted endpoint is listed for DeepEval. LangSmith API + MCP has a hosted endpoint at https://api.smith.langchain.com.

### Are DeepEval and LangSmith API + MCP open source?

DeepEval is open source (Apache 2.0 for the Python and TypeScript packages and the agent skills. Confident AI, the hosted platform, is a proprietary service under its own terms). No open-source release is listed for LangSmith API + MCP.


## For agents

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

## Other comparisons with DeepEval or LangSmith API + MCP

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- [Arize Phoenix vs LangSmith API + MCP](https://www.anchorterminal.com/compare/arize-phoenix-vs-langsmith.md)
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- [DeepEval vs Langfuse API + MCP](https://www.anchorterminal.com/compare/deepeval-vs-langfuse.md)
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- [DeepEval vs Prefactor](https://www.anchorterminal.com/compare/deepeval-vs-prefactor.md)
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