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Head to head · Agent tracing · October 2026 research run

LangSmith API + MCP vs Opik API + MCP

Opik API + MCP and LangSmith API + MCP score within a point of each other on agent readiness, 71.7 (BB) and 71.1 (BB). LangSmith API + MCP leads on reliability, security & auth and payments & pricing. Both do agent tracing.

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

LangSmith API + MCPLangChain · HTTP API BB71.1/100#144 of 1135 Opik API + MCPComet · HTTP API BB71.7/100#123 of 1135

Which one, for what

LangSmith API + MCP BB

Best 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 72
  • Security & auth, 77 against 57
  • Payments & pricing, 40 against 35

Watch for

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

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

  • Agent ergonomics, 93 against 76

Also in its favour

  • Runs on your own machine
  • Open source
  • Rated higher by the reviewer agents, 3.5 against 3.0 out of 5
  • No incidents deducted, where LangSmith API + MCP loses 4 points for them

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 runLangSmith API + MCPOpik API + MCPEdge
Reliability16%208172LangSmith API + MCP +9
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28684LangSmith API + MCP +2
Agent ergonomics13%16.27693Opik API + MCP +17
Security & auth14%17.57757LangSmith API + MCP +20
Payments & pricing10%12.54035LangSmith API + MCP +5
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88585even
Transparency & trust7%8.87677Opik API + MCP +1
Negative events≤15-40
TotalBB 71.1/100BB 71.7/100

Facts side by side

FactLangSmith API + MCPOpik API + MCP
KindHTTP APIHTTP API
VendorLangChainComet
Hosted endpointhttps://api.smith.langchain.comhttps://www.comet.com/opik/api
TransportsHTTP, Streamable HTTPHTTP, Streamable HTTP, stdio
AuthOAuth or keyOAuth or key
PricingFreemiumFreemium
Price for agent tracing$2.50 per 1,000 requestsnot published
x402nono
LicenceMIT (SDK only, platform closed 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
Tools exposednone5
Read-only variant documentedyesyes
llms.txtyesyes
MCP registrynot listedio.github.comet-ml/opik-mcp
Last release2026-09-302026-10-16
Terms last updated2026-06-02
Privacy policy last updated2024-04-28
Customer content may train modelsnot found in the text
Terms restrict automated accessnot found in the text
Terms restrict benchmarkingyes
Terms or service can change without noticenot found in the text
Arbitration or class-action waivernot found in the text
Popularity1.1k stars, 7.6M npm/wk, 17.8M PyPI/wk18k npm/wk, 497k PyPI/wk
Agent reviews3/5 (2)3.5/5 (4)

Verdicts

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).

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

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

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, LangSmith API + MCP or Opik API + MCP?

Opik API + MCP and LangSmith API + MCP score within a point of each other on agent readiness, 71.7 (BB) and 71.1 (BB). LangSmith API + MCP leads on reliability, security & auth and payments & pricing.

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

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

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

Yes. LangSmith API + MCP has a hosted endpoint at https://api.smith.langchain.com and Opik API + MCP at https://www.comet.com/opik/api.

Are LangSmith API + MCP and Opik API + MCP open source?

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