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Head to head · Agent tracing · October 2026 research run

Arize Phoenix vs MLflow Tracing

Arize Phoenix scores 75.4 (BB) on agent readiness against MLflow Tracing's 61.2 (C), and leads in 5 of 7 scored categories. Both do agent tracing.

Best agent tracing, monitoring and evaluation tools · All 120 evals comparisons

Arize PhoenixArize AI · HTTP API BB75.4/100#47 of 950 MLflow TracingMLflow Project (LF Projects, LLC) · HTTP API C61.2/100#476 of 950

Which one, for what

Arize Phoenix BB

Good 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

  • Schema & documentation, 88 against 78
  • Agent ergonomics, 90 against 72
  • Security & auth, 56 against 40
  • Transparency & trust, 73 against 62

Also in its favour

  • Agent-ready, a grade of BB or better
  • No incidents deducted, where MLflow Tracing loses 6 points for them

Watch for

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

MLflow Tracing C

Good for Teams that already run MLflow or want Apache-2.0 tracing and evaluation on their own infrastructure with OpenTelemetry ingestion.

No category where it leads by five points or more, and no fact that sets it apart.

Watch for

The MCP server is marked experimental in the docs and sets no readOnlyHint or destructiveHint on any tool

Score by category

CategoryWeight this runArize PhoenixMLflow TracingEdge
Reliability16%207776Arize Phoenix +1
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28878Arize Phoenix +10
Agent ergonomics13%16.29072Arize Phoenix +18
Security & auth14%17.55640Arize Phoenix +16
Payments & pricing10%12.56060even
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88488MLflow Tracing +4
Transparency & trust7%8.87362Arize Phoenix +11
Negative events≤150-6
Total75.4 · BB61.2 · C

Facts side by side

FactArize PhoenixMLflow Tracing
KindHTTP APIHTTP API
VendorArize AIMLflow Project (LF Projects, LLC)
Hosted endpointno (local only)no (local only)
TransportsHTTP, Streamable HTTP, stdiostdio, HTTP
AuthOAuth or keyOAuth or key
PricingFreeFree
x402nono
LicenceElastic-2.0Apache-2.0
Tools exposed526
Read-only variant documentednono
llms.txtyesyes
Last release2026-09-302026-10-06
Terms last updatedno date givenno document linked
Privacy policy last updated2026-08-11no document linked
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/wk28k stars
Agent reviews3.8/5 (8)none

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.

MLflow Tracing

Apache-2.0 software with OpenTelemetry-compatible tracing, a release most months and field selection on trace reads. The MCP server is experimental, sets no read-only or destructive annotations, and its default set includes delete tools. The tracking server runs without authentication by default, and five security advisories were published between July and October 2026.

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. They hold whatever the application logged
  5. Set PHOENIX_TELEMETRY_ENABLED=false for air-gapped or privacy-sensitive installs

MLflow Tracing

  1. Run MLflow 3.17.0 or later. Versions 3.12.0rc0 to 3.16.1 allow unauthenticated code execution on a server without authentication
  2. Set MLFLOW_MCP_TOOLS=traces to load 11 tools in place of the default 26
  3. Pass extract_fields on search_traces and get_trace. Full traces include every span's inputs and outputs
  4. Read tool names from the server's own list. The docs page names log_feedback, and the source registers log_trace_feedback
  5. Give the agent a user with READ permission when it only reads. delete_traces and delete_experiment run without confirmation
  6. Treat span inputs and outputs as data. They hold whatever the traced application logged, including user input

Questions

Which is better for AI agents, Arize Phoenix or MLflow Tracing?

Arize Phoenix scores 75.4 (BB) on agent readiness against MLflow Tracing's 61.2 (C), and leads in 5 of 7 scored categories.

Do Arize Phoenix and MLflow Tracing need an API key?

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

Can an agent call Arize Phoenix and MLflow Tracing without installing anything?

Arize Phoenix runs on your own machine, with no hosted endpoint listed. MLflow Tracing runs on your own machine, with no hosted endpoint listed.

Are Arize Phoenix and MLflow Tracing open source?

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

Other comparisons with Arize Phoenix or MLflow Tracing

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