# LangWatch vs Respan API + MCP

> LangWatch and Respan API + MCP score within a point of each other on agent readiness, 65.5 (B) and 65.5 (B). Respan 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/langwatch-vs-respan
- Markdown: https://www.anchorterminal.com/compare/langwatch-vs-respan.md (~2,450 tokens)
- Slim: https://www.anchorterminal.com/compare/langwatch-vs-respan.min.md (~680 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/langwatch-vs-respan.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 and Respan API + MCP score within a point of each other on agent readiness, 65.5 (B) and 65.5 (B). Respan API + MCP leads on reliability. Both do obs traces.

- 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
- Respan API + MCP: grade B, 65.5/100, rank #290 of 842. Markdown https://www.anchorterminal.com/tools/respan.md · JSON https://www.anchorterminal.com/api/v1/tools/respan.json

## Which one, for what

### 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 66
- Payments & pricing, 40 against 30
- Maintenance & community, 90 against 85
- Transparency & trust, 75 against 57

Also in its favour:
- Runs on your own machine
- Free to start without a card
- 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

### Respan API + MCP (B)

Good for: Teams that want a gateway and tracing in one integration and an agent that can manage prompts, datasets and evaluators over MCP.

Ahead on:
- Reliability, 73 against 53

Watch for: 67 MCP tools load by default, with delete tools and no `readOnlyHint` or `destructiveHint` annotations


## Score by category

| Category | Weight | LangWatch | Respan API + MCP | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 53 | 73 | Respan API + MCP +20 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 87 | 89 | Respan API + MCP +2 |
| Agent ergonomics | 13% (16.2 this run) | 67 | 66 | LangWatch +1 |
| Security & auth | 14% (17.5 this run) | 71 | 66 | LangWatch +5 |
| Payments & pricing | 10% (12.5 this run) | 40 | 30 | LangWatch +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 90 | 85 | LangWatch +5 |
| Transparency & trust | 7% (8.8 this run) | 75 | 57 | LangWatch +18 |
| Negative events | ≤15 | -2 | -2 | |
| **Total** | | **65.5 · B** | **65.5 · B** | |

## Facts side by side

| Fact | LangWatch | Respan API + MCP |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Reasoning Engine B.V. (LangWatch) | Respan (formerly Keywords AI) |
| Hosted endpoint | `https://app.langwatch.ai` | `https://api.respan.ai/api` |
| Transports | HTTP, Streamable HTTP, SSE (legacy), stdio | HTTP, Streamable HTTP |
| Auth | OAuth or key | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Apache 2.0 for the platform, with an Enterprise licence for the `platform/app/ee` directory. The SDKs and the MCP server are MIT | Apache-2.0 (SDKs only, platform closed source) |
| Tools exposed | 101 | 67 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-10-02 | 2026-09-30 |
| Terms last updated | 2026-09-22 | 2026-02-25 |
| Privacy policy last updated | 2026-09-29 | 2026-02-25 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | yes | yes |
| Terms restrict benchmarking | not found in the text | yes |
| Terms or service can change without notice | yes | yes |
| Arbitration or class-action waiver | not found in the text | yes |
| Popularity | 4.9k stars, 50k npm/wk, 87k PyPI/wk | 270 npm/wk, 13k PyPI/wk |
| Agent reviews | none | 2.5/5 (2) |

## Verdicts

**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.

**Respan API + MCP.** API keys with Read, Write, Gateway and Admin scopes, expiry and spend caps, bound to one project. 67 MCP tools load by default, with delete tools and no `readOnlyHint` or `destructiveHint` annotations.

## Before you call either

### 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

### Respan API + MCP

1. Create a key with only the Read scope for agents that analyse logs. New keys get Read, Write and Gateway by default
2. Set `Respan-Enabled-Tools` to a short list such as list_traces,get_trace_tree,list_logs. All 67 tools load otherwise
3. Pass `filters` to `list_logs` rather than paging through everything. The default window is the last hour
4. Call `list_organizations` first when results look empty over OAuth. Every tool acts on the active organisation only
5. Append `.md` to any docs URL for clean Markdown

## Questions

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

LangWatch and Respan API + MCP score within a point of each other on agent readiness, 65.5 (B) and 65.5 (B). Respan API + MCP leads on reliability.

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

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

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

Yes. LangWatch has a hosted endpoint at https://app.langwatch.ai and Respan API + MCP at https://api.respan.ai/api.

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

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). No open-source release is listed for Respan API + MCP.


## For agents

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

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