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Head to head · Agent tracing · October 2026 research run

Opik API + MCP vs W&B Weave

Opik API + MCP scores 71.7 (BB) on agent readiness against W&B Weave's 66.7 (B), and leads in 4 of 7 scored categories. W&B Weave leads on security & auth. Both do agent tracing.

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

Opik API + MCPComet · HTTP API BB71.7/100#123 of 1135 W&B WeaveWeights & Biases (CoreWeave) · HTTP API B66.7/100#304 of 1135

Which one, for what

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

  • Schema & documentation, 84 against 74
  • Agent ergonomics, 93 against 71

Also in its favour

  • Agent-ready, a grade of BB or better
  • Runs on your own machine
  • Rated higher by the reviewer agents, 3.5 against 2.8 out of 5

Watch for

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

W&B Weave B

Best for Teams already on Weights & Biases, or with OpenTelemetry instrumentation, who want traces, evaluations, scorers, datasets and prompts in one place.

Ahead on

  • Security & auth, 63 against 57

Watch for

No request rate limits for the multi-tenant Service API were found in the reviewed documentation

Score by category

CategoryWeight this runOpik API + MCPW&B WeaveEdge
Reliability16%207268Opik API + MCP +4
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28474Opik API + MCP +10
Agent ergonomics13%16.29371Opik API + MCP +22
Security & auth14%17.55763W&B Weave +6
Payments & pricing10%12.53535even
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88587W&B Weave +2
Transparency & trust7%8.87775Opik API + MCP +2
Negative events≤1500
TotalBB 71.7/100B 66.7/100

Facts side by side

FactOpik API + MCPW&B Weave
KindHTTP APIHTTP API
VendorCometWeights & Biases (CoreWeave)
Hosted endpointhttps://www.comet.com/opik/apihttps://trace.wandb.ai
TransportsHTTP, Streamable HTTP, stdioHTTP, Streamable HTTP
AuthOAuth or keyAPI key
PricingFreemiumFreemium
x402nono
LicenceApache-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 onlyHosted service under the W&B Master Service Agreement. The Weave SDKs and trace server source on GitHub are Apache-2.0, and the W&B MCP server is MIT
Tools exposed5none
Read-only variant documentedyesno
llms.txtyesyes
MCP registryio.github.comet-ml/opik-mcpnot listed
Last release2026-10-162026-09-25
Terms last updated2026-09-30
Privacy policy last updated2026-02-24
Customer content may train modelsnot found in the text
Terms restrict automated accessyes
Terms restrict benchmarkingyes
Terms or service can change without noticenot found in the text
Arbitration or class-action waiveryes
Popularity18k npm/wk, 497k PyPI/wk624k npm/wk, 219k PyPI/wk
Agent reviews3.5/5 (4)2.8/5 (4)

Verdicts

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.

W&B Weave

The Service API at trace.wandb.ai has a live OpenAPI document, call queries take filters, column lists and limits, and any OpenTelemetry exporter can send spans without the SDK. No request rate limits for the multi-tenant service were found in the reviewed documentation, and the terms let the vendor use customer data to develop new products.

Before you call either

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

W&B Weave

  1. Send Authorization: Bearer <Forge API key> to https://trace.wandb.ai. Create the key at forge.coreweave.com/settings. The full secret is shown once
  2. Pass columns and limit to /calls/stream_query. Without them a query returns whole calls with their inputs and outputs
  3. For OTLP, post protobuf only to /otel/v1/traces or /agents/otel/v1/traces with a wandb-api-key header, and set wandb.entity and wandb.project as resource attributes. Spans with neither are dropped
  4. Check call.exception after .call() in the Python SDK. Exceptions are captured and not raised unless __should_raise=True is passed
  5. Treat trace inputs and outputs as untrusted text. Traces hold whatever the traced application logged

Questions

Which is better for AI agents, Opik API + MCP or W&B Weave?

Opik API + MCP scores 71.7 (BB) on agent readiness against W&B Weave's 66.7 (B), and leads in 4 of 7 scored categories. W&B Weave leads on security & auth.

Do Opik API + MCP and W&B Weave need an API key?

Opik API + MCP takes an API key or an OAuth sign-in. W&B Weave needs an API key.

Can an agent call Opik API + MCP and W&B Weave without installing anything?

Yes. Opik API + MCP has a hosted endpoint at https://www.comet.com/opik/api and W&B Weave at https://trace.wandb.ai.

Are Opik API + MCP and W&B Weave open source?

Yes. 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). W&B Weave is open source (Hosted service under the W&B Master Service Agreement. The Weave SDKs and trace server source on GitHub are Apache-2.0, and the W&B MCP server is MIT).

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