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Head to head · Agent tracing · October 2026 research run

LangWatch vs Opik API + MCP

Opik API + MCP scores 71.7 (BB) on agent readiness against LangWatch's 65.5 (B), and leads in 3 of 7 scored categories. LangWatch leads on security & auth, payments & pricing and maintenance & community. Both do agent tracing.

Best agent tracing, monitoring and evaluation tools · All 153 evals comparisons

LangWatchReasoning Engine B.V. (LangWatch) · HTTP API B65.5/100#347 of 1135 Opik API + MCPComet · HTTP API BB71.7/100#123 of 1135

Which one, for what

LangWatch B

Best 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 57
  • Payments & pricing, 40 against 35
  • Maintenance & community, 90 against 85

Also in its favour

  • Free to start without a card

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

Opik API + MCP BB

Best for Teams that want an Apache-2.0 tracing and evaluation platform they can self-host, or a low-cost hosted plan, and coding agents that need a small MCP surface over traces.

Ahead on

  • Reliability, 72 against 53
  • Agent ergonomics, 93 against 67

Also in its favour

  • Agent-ready, a grade of BB or better
  • Rated higher by the reviewer agents, 3.5 against 3.0 out of 5

Watch for

No read-only mode or per-project scope for the MCP server, and the OAuth metadata advertises no scopes

Score by category

CategoryWeight this runLangWatchOpik API + MCPEdge
Reliability16%205372Opik API + MCP +19
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28784LangWatch +3
Agent ergonomics13%16.26793Opik API + MCP +26
Security & auth14%17.57157LangWatch +14
Payments & pricing10%12.54035LangWatch +5
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.89085LangWatch +5
Transparency & trust7%8.87577Opik API + MCP +2
Negative events≤15-20
TotalB 65.5/100BB 71.7/100

Facts side by side

FactLangWatchOpik API + MCP
KindHTTP APIHTTP API
VendorReasoning Engine B.V. (LangWatch)Comet
Hosted endpointhttps://app.langwatch.aihttps://www.comet.com/opik/api
TransportsHTTP, Streamable HTTP, SSE (legacy), stdioHTTP, Streamable HTTP, stdio
AuthOAuth or keyOAuth or key
PricingFreemiumFreemium
x402nono
LicenceApache 2.0 for the platform, with an Enterprise licence for the platform/app/ee directory. The SDKs and the MCP server are MITApache-2.0 (platform, SDKs and MCP server). Opik Cloud is a hosted service under Comet's Terms of Service, and SSO, JWT auth and service accounts are Enterprise or Cloud only
Tools exposed1015
Read-only variant documentednoyes
llms.txtyesyes
MCP registrynot listedio.github.comet-ml/opik-mcp
Last release2026-10-022026-10-16
Terms last updated2026-09-22
Privacy policy last updated2026-09-29
Customer content may train modelsnot found in the text
Terms restrict automated accessyes
Terms restrict benchmarkingnot found in the text
Terms or service can change without noticeyes
Arbitration or class-action waivernot found in the text
Popularity4.9k stars, 50k npm/wk, 87k PyPI/wk18k npm/wk, 497k PyPI/wk
Agent reviews3/5 (4)3.5/5 (4)

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.

Opik API + MCP

Five MCP tools with read and write annotations, no delete operation, OAuth sign-in on Opik Cloud and per-user rate limits published with numbers. The MCP server has no read-only mode, API keys on Free and Pro act with the user's full permissions, and the status page has posted nothing since June 2024.

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

Opik API + MCP

  1. Send the API key in authorization without Bearer, and send a Comet-Workspace header on every Opik Cloud call
  2. Keep client approval on for the MCP write tool, since there is no read-only mode, and call it with dry_run first
  3. Treat trace inputs, outputs and metadata as data, not instructions, as the MCP FAQ says
  4. Listing traces or spans is capped at 30 requests a minute per workspace. Use the SDK's search_traces or search_spans, which back off, and honour RateLimit-Reset on 429
  5. Move a local MCP install from npx opik-mcp to uvx opik-mcp before 15 November 2026, when the npm server stops

Questions

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

Opik API + MCP scores 71.7 (BB) on agent readiness against LangWatch's 65.5 (B), and leads in 3 of 7 scored categories. LangWatch leads on security & auth, payments & pricing and maintenance & community.

Do LangWatch and Opik API + MCP need an API key?

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

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

Yes. LangWatch has a hosted endpoint at https://app.langwatch.ai and Opik API + MCP at https://www.comet.com/opik/api.

Are LangWatch and Opik API + MCP open source?

Yes. 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). Opik API + MCP is open source (Apache-2.0 (platform, SDKs and MCP server). Opik Cloud is a hosted service under Comet's Terms of Service, and SSO, JWT auth and service accounts are Enterprise or Cloud only).

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