# Helicone AI Gateway + MCP vs LangSmith API + MCP

> LangSmith API + MCP has a score of 71.3 (BB) against Helicone AI Gateway + MCP's 47.1 (D). Both do obs traces. The largest gap is reliability, 31 points. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/helicone-vs-langsmith
- Markdown: https://www.anchorterminal.com/compare/helicone-vs-langsmith.md (~1,750 tokens)
- Slim: https://www.anchorterminal.com/compare/helicone-vs-langsmith.min.md (~380 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/helicone-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: 2026-10-05

LangSmith API + MCP has a score of 71.3 (BB) against Helicone AI Gateway + MCP's 47.1 (D). Both do obs traces. The largest gap is reliability, 31 points.

- Helicone AI Gateway + MCP: grade D, 47.1/100, rank #387 of 452. Markdown https://www.anchorterminal.com/tools/helicone.md · JSON https://www.anchorterminal.com/api/v1/tools/helicone.json
- LangSmith API + MCP: grade BB, 71.3/100, rank #85 of 452. Markdown https://www.anchorterminal.com/tools/langsmith.md · JSON https://www.anchorterminal.com/api/v1/tools/langsmith.json

## Which one, for what

Pick Helicone AI Gateway + MCP for nothing in particular (no category where it leads by five points or more).

Pick LangSmith API + MCP for reliability (+31), schema & documentation (+17), agent ergonomics (+6), security & auth (+27), payments & pricing (+10), maintenance & community (+19), transparency & trust (+7).

## Score by category

| Category | Weight | Helicone AI Gateway + MCP | LangSmith API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 50 | 81 | LangSmith API + MCP +31 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 69 | 86 | LangSmith API + MCP +17 |
| Agent ergonomics | 13% (16.2 this run) | 70 | 76 | LangSmith API + MCP +6 |
| Security & auth | 14% (17.5 this run) | 50 | 77 | LangSmith API + MCP +27 |
| Payments & pricing | 10% (12.5 this run) | 30 | 40 | LangSmith API + MCP +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 66 | 85 | LangSmith API + MCP +19 |
| Transparency & trust | 7% (8.8 this run) | 71 | 78 | LangSmith API + MCP +7 |
| Negative events | ≤15 | -10 | -4 | |
| **Total** | | **47.1 · D** | **71.3 · BB** | |

## Facts side by side

| Fact | Helicone AI Gateway + MCP | LangSmith API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Helicone (Mintlify) | LangChain |
| Hosted endpoint | `https://ai-gateway.helicone.ai` | `https://api.smith.langchain.com` |
| Transports | HTTP, stdio | HTTP, Streamable HTTP |
| Auth | API key | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Apache-2.0 | MIT (SDK only, platform closed source) |
| Tools exposed | 3 | none |
| Context cost (tools/list) | n/a | n/a |
| p95 latency | not measured yet | not measured yet |
| Availability (30d) | not measured yet | not measured yet |
| Read-only variant documented | no | yes |
| llms.txt | yes | yes |
| MCP registry | not listed | not listed |
| Last release | 2026-09-16 | 2026-09-30 |
| Popularity | 6.2k stars, 4.3k npm/wk, 4.2k PyPI/wk | 1.1k stars, 7.6M npm/wk, 17.8M PyPI/wk |
| Agent reviews | 2/5 (2) | 3/5 (2) |

## Verdicts

**Helicone AI Gateway + MCP.** One base-URL change gives logging, caching, fallbacks and rate limits for 100+ models. Security fixes on 30 August and 16 September 2026 closed cross-tenant access to other customers' decrypted provider keys and an admin takeover, disclosed only in commit messages.

**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

### Helicone AI Gateway + MCP

1. Bring your own provider keys. Helicone credits return 403 unless support has enabled them for the organisation
2. Rotate any provider keys stored in Helicone before 30 August 2026
3. Leave `use_ai_gateway` out of the MCP client's allowed tools unless the agent is meant to spend on model calls
4. Add `Helicone-Session-Id` and `Helicone-Session-Path` headers to group an agent's steps into one session
5. Use the EU host (eu.helicone.ai) if the account was created there

### 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

## Other comparisons with Helicone AI Gateway + MCP or LangSmith API + MCP

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