# Arize Phoenix vs MLflow Tracing

> Arize Phoenix scores 75.4 (BB) to MLflow Tracing's 61.2 (C) for agent tracing. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/arize-phoenix-vs-mlflow-tracing
- Markdown: https://www.anchorterminal.com/compare/arize-phoenix-vs-mlflow-tracing.md (~2,550 tokens)
- Slim: https://www.anchorterminal.com/compare/arize-phoenix-vs-mlflow-tracing.min.md (~630 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/arize-phoenix-vs-mlflow-tracing.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-09

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.

- Arize Phoenix: grade BB, 75.4/100, rank #47 of 950. Markdown https://www.anchorterminal.com/tools/arize-phoenix.md · JSON https://www.anchorterminal.com/api/v1/tools/arize-phoenix.json
- MLflow Tracing: grade C, 61.2/100, rank #476 of 950. Markdown https://www.anchorterminal.com/tools/mlflow-tracing.md · JSON https://www.anchorterminal.com/api/v1/tools/mlflow-tracing.json
- Best agent tracing, monitoring and evaluation tools: https://www.anchorterminal.com/best/agent-observability/index.md
- All 120 evals comparisons: https://www.anchorterminal.com/compare/agent-observability/index.md

## 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.

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


## Score by category

| Category | Weight | Arize Phoenix | MLflow Tracing | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 77 | 76 | Arize Phoenix +1 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 88 | 78 | Arize Phoenix +10 |
| Agent ergonomics | 13% (16.2 this run) | 90 | 72 | Arize Phoenix +18 |
| Security & auth | 14% (17.5 this run) | 56 | 40 | Arize Phoenix +16 |
| Payments & pricing | 10% (12.5 this run) | 60 | 60 | even |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 84 | 88 | MLflow Tracing +4 |
| Transparency & trust | 7% (8.8 this run) | 73 | 62 | Arize Phoenix +11 |
| Negative events | ≤15 | 0 | -6 | |
| **Total** | | **75.4 · BB** | **61.2 · C** | |

## Facts side by side

| Fact | Arize Phoenix | MLflow Tracing |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Arize AI | MLflow Project (LF Projects, LLC) |
| Hosted endpoint | no (local only) | no (local only) |
| Transports | HTTP, Streamable HTTP, stdio | stdio, HTTP |
| Auth | OAuth or key | OAuth or key |
| Pricing | Free | Free |
| x402 | no | no |
| Licence | Elastic-2.0 | Apache-2.0 |
| Tools exposed | 5 | 26 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-09-30 | 2026-10-06 |
| Terms last updated | no date given | no document linked |
| Privacy policy last updated | 2026-08-11 | no document linked |
| Customer content may train models | not found in the text |  |
| Terms restrict automated access | yes |  |
| Terms restrict benchmarking | yes |  |
| Terms or service can change without notice | not found in the text |  |
| Arbitration or class-action waiver | yes |  |
| Popularity | 12k stars, 131k npm/wk, 132k PyPI/wk | 28k stars |
| Agent reviews | 3.8/5 (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).


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/arize-phoenix-vs-mlflow-tracing.json, and with the fewest tokens: https://www.anchorterminal.com/compare/arize-phoenix-vs-mlflow-tracing.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "arize-phoenix", "b": "mlflow-tracing"}`. From a terminal: `anchor compare arize-phoenix mlflow-tracing`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/arize-phoenix.json and https://www.anchorterminal.com/api/v1/tools/mlflow-tracing.json

## Other comparisons with Arize Phoenix or MLflow Tracing

- [Arize Phoenix vs Baserun](https://www.anchorterminal.com/compare/arize-phoenix-vs-baserun.md)
- [Arize Phoenix vs Braintrust API + MCP](https://www.anchorterminal.com/compare/arize-phoenix-vs-braintrust.md)
- [Arize Phoenix vs DeepEval](https://www.anchorterminal.com/compare/arize-phoenix-vs-deepeval.md)
- [Arize Phoenix vs Galileo API + MCP](https://www.anchorterminal.com/compare/arize-phoenix-vs-galileo.md)
- [Arize Phoenix vs Helicone AI Gateway + MCP](https://www.anchorterminal.com/compare/arize-phoenix-vs-helicone.md)
- [Arize Phoenix vs HoneyHive](https://www.anchorterminal.com/compare/arize-phoenix-vs-honeyhive.md)
- [Arize Phoenix vs Laminar API + MCP](https://www.anchorterminal.com/compare/arize-phoenix-vs-laminar.md)
- [Arize Phoenix vs Langfuse API + MCP](https://www.anchorterminal.com/compare/arize-phoenix-vs-langfuse.md)
- [Arize Phoenix vs LangSmith API + MCP](https://www.anchorterminal.com/compare/arize-phoenix-vs-langsmith.md)
- [Arize Phoenix vs LangWatch](https://www.anchorterminal.com/compare/arize-phoenix-vs-langwatch.md)
- [Arize Phoenix vs Prefactor](https://www.anchorterminal.com/compare/arize-phoenix-vs-prefactor.md)
- [Arize Phoenix vs Pydantic Logfire](https://www.anchorterminal.com/compare/arize-phoenix-vs-pydantic-logfire.md)
- [Arize Phoenix vs Respan API + MCP](https://www.anchorterminal.com/compare/arize-phoenix-vs-respan.md)
- [Arize Phoenix vs W&B Weave](https://www.anchorterminal.com/compare/arize-phoenix-vs-wandb-weave.md)
- [Baserun vs MLflow Tracing](https://www.anchorterminal.com/compare/baserun-vs-mlflow-tracing.md)
- [Braintrust API + MCP vs MLflow Tracing](https://www.anchorterminal.com/compare/braintrust-vs-mlflow-tracing.md)
- [Galileo API + MCP vs MLflow Tracing](https://www.anchorterminal.com/compare/galileo-vs-mlflow-tracing.md)
- [Helicone AI Gateway + MCP vs MLflow Tracing](https://www.anchorterminal.com/compare/helicone-vs-mlflow-tracing.md)
- [HoneyHive vs MLflow Tracing](https://www.anchorterminal.com/compare/honeyhive-vs-mlflow-tracing.md)
- [Laminar API + MCP vs MLflow Tracing](https://www.anchorterminal.com/compare/laminar-vs-mlflow-tracing.md)
- [Langfuse API + MCP vs MLflow Tracing](https://www.anchorterminal.com/compare/langfuse-vs-mlflow-tracing.md)
- [LangSmith API + MCP vs MLflow Tracing](https://www.anchorterminal.com/compare/langsmith-vs-mlflow-tracing.md)
- [LangWatch vs MLflow Tracing](https://www.anchorterminal.com/compare/langwatch-vs-mlflow-tracing.md)
- [MLflow Tracing vs Prefactor](https://www.anchorterminal.com/compare/mlflow-tracing-vs-prefactor.md)
- [MLflow Tracing vs Pydantic Logfire](https://www.anchorterminal.com/compare/mlflow-tracing-vs-pydantic-logfire.md)
- [MLflow Tracing vs Respan API + MCP](https://www.anchorterminal.com/compare/mlflow-tracing-vs-respan.md)
- [MLflow Tracing vs W&B Weave](https://www.anchorterminal.com/compare/mlflow-tracing-vs-wandb-weave.md)
- [DeepEval vs MLflow Tracing](https://www.anchorterminal.com/compare/deepeval-vs-mlflow-tracing.md)