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Head to head · Agent tracing · October 2026 research run

Arize Phoenix vs Opik API + MCP

Arize Phoenix scores 75.7 (BB) on agent readiness against Opik API + MCP's 71.7 (BB), and leads in 4 of 7 scored categories. Both do agent tracing.

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

Arize PhoenixArize AI · HTTP API BB75.7/100#47 of 1135 Opik API + MCPComet · HTTP API BB71.7/100#123 of 1135

Which one, for what

Arize Phoenix BB

Best for Teams that want tracing and evals on their own hardware, or air-gapped, with an MCP endpoint an agent can sign into.

Ahead on

  • Reliability, 77 against 72
  • Payments & pricing, 60 against 35

Watch for

Auth is off by default and the default admin password is admin

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.

Also in its favour

  • A hosted endpoint, with nothing to install

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 runArize PhoenixOpik API + MCPEdge
Reliability16%207772Arize Phoenix +5
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28884Arize Phoenix +4
Agent ergonomics13%16.29093Opik API + MCP +3
Security & auth14%17.55857Arize Phoenix +1
Payments & pricing10%12.56035Arize Phoenix +25
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88485Opik API + MCP +1
Transparency & trust7%8.87377Opik API + MCP +4
Negative events≤1500
TotalBB 75.7/100BB 71.7/100

Facts side by side

FactArize PhoenixOpik API + MCP
KindHTTP APIHTTP API
VendorArize AIComet
Hosted endpointno (local only)https://www.comet.com/opik/api
TransportsHTTP, Streamable HTTP, stdioHTTP, Streamable HTTP, stdio
AuthOAuth or keyOAuth or key
PricingFreeFreemium
x402nono
LicenceElastic-2.0Apache-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 exposed55
Read-only variant documentednoyes
llms.txtyesyes
MCP registrynot listedio.github.comet-ml/opik-mcp
Last release2026-10-162026-10-16
Terms last updatedno date given
Privacy policy last updated2026-08-11
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
Popularity12k stars, 131k npm/wk, 132k PyPI/wk18k npm/wk, 497k PyPI/wk
Agent reviews3.8/5 (8)3.5/5 (4)

Verdicts

Arize Phoenix

Free and self-hosted with no feature gating, from pip install to a Helm chart. Auth is off by default and the default admin password is admin.

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

Arize Phoenix

  1. Turn on auth before exposing the server, and change the admin password
  2. Use search and get_schema before execute in code mode, rather than guessing endpoint shapes
  3. Give the agent a viewer account if it only needs to read traces
  4. Treat span inputs and outputs as data, as the MCP docs say. They hold whatever the application logged, including user input
  5. Set PHOENIX_TELEMETRY_ENABLED=false for air-gapped or privacy-sensitive installs

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, Arize Phoenix or Opik API + MCP?

Arize Phoenix scores 75.7 (BB) on agent readiness against Opik API + MCP's 71.7 (BB), and leads in 4 of 7 scored categories.

Do Arize Phoenix and Opik API + MCP need an API key?

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

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

Arize Phoenix runs on your own machine, with no hosted endpoint listed. Opik API + MCP has a hosted endpoint at https://www.comet.com/opik/api.

Are Arize Phoenix and Opik API + MCP open source?

Yes. Arize Phoenix is open source (Elastic-2.0). 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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