MCPInstall

phoenix-evals

Build, run, and validate evaluators for AI/LLM applications with Phoenix, in Python or TypeScript (including Vercel AI SDK apps) — code-based checks and LLM-as-a-judge, run over exported traces or dataframes or as Phoenix experiments, gate them in CI, and validate judges against human-labeled data.

Installs
1.6K
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Install

Works with every agent the skills CLI supports.

npx skills add https://github.com/arize-ai/phoenix --skill phoenix-evals
  1. 01

    Install

    Run the command in your project. The CLI asks which agents to install for.

  2. 02

    Describe the task

    Ask your agent for something this skill covers. It loads phoenix-evals automatically when relevant.

  3. 03

    Review the result

    The agent follows the SKILL.md steps, scripts and references bundled with the skill.

SKILL.md

The instructions your agent reads when the skill is triggered.

Phoenix Evals

Build evaluators for AI/LLM applications. Code first, LLM for nuance, validate against humans.

Quick Reference

TaskFiles
Setupsetup-python, setup-typescript
Decide what to evaluateevaluators-overview
Choose a judge modelfundamentals-model-selection
Use pre-built evaluatorsevaluators-pre-built
Build code evaluatorevaluators-code-python, evaluators-code-typescript
Build LLM evaluatorevaluators-llm-python, evaluators-llm-typescript, evaluators-custom-templates
Batch evaluate DataFrameevaluate-dataframe-python
Run experimentexperiments-running-python, experiments-running-typescript
Run evals in a test runner (CI gate)integrations-pytest, integrations-vitest-jest
Create datasetexperiments-datasets-python, experiments-datasets-typescript
Generate synthetic dataexperiments-synthetic-python, experiments-synthetic-typescript
Validate evaluator accuracyvalidation, validation-evaluators-python, validation-evaluators-typescript
Export spansobserve-tracing-setup
Write a span filter (SpanQuery().where)filter-expressions
Sample traces for reviewobserve-sampling-python, observe-sampling-typescript
Analyze errorserror-analysis, error-analysis-multi-turn, axial-coding
RAG evalsevaluators-rag
Avoid common mistakescommon-mistakes-python, fundamentals-anti-patterns
Productionproduction-overview, production-guardrails, production-continuous

Workflows

Starting Fresh: observe-tracing-setup → error-analysis → axial-coding → evaluators-overview

Building Evaluator: fundamentals → common-mistakes-python → evaluators-{code|llm}-{python|typescript} → validation-evaluators-{python|typescript}

RAG Systems: evaluators-rag → evaluators-code-* (retrieval) → evaluators-llm-* (faithfulness)

Gating CI: evaluators-{code|llm}-{python|typescript} → integrations-{pytest|vitest-jest} → production-continuous

Production: production-overview → production-guardrails → production-continuous

Reference Categories

PrefixDescription
fundamentals-*Types, scores, anti-patterns
observe-*Tracing, sampling
error-analysis-*Finding failures
axial-coding-*Categorizing failures
evaluators-*Code, LLM, RAG evaluators
experiments-*Datasets, running experiments
integrations-*Run evals from test runners (pytest, Vitest, Jest) as a CI gate
validation-*Validating evaluator accuracy against human labels
production-*CI/CD, monitoring

Key Principles

PrincipleAction
Error analysis firstCan't automate what you haven't observed
Custom > genericBuild from your failures
Code firstDeterministic before LLM
Validate judges>80% accuracy, >70% TPR/TNR
Binary > LikertPass/fail, not 1-5
Invariants gate, signals trendassert/expect hard invariants (CI red); log LLM-judge quality signals and gate the aggregate (acceptance criteria), not every case

FAQ

What does the phoenix-evals skill do?

Build, run, and validate evaluators for AI/LLM applications with Phoenix, in Python or TypeScript (including Vercel AI SDK apps) — code-based checks and LLM-as-a-judge, run over exported traces or dataframes or as Phoenix experiments, gate them in CI, and validate judges against human-labeled data.

How do I install phoenix-evals?

Run npx skills add https://github.com/arize-ai/phoenix --skill phoenix-evals in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/phoenix-evals/ (personal) or .claude/skills/phoenix-evals/ (project).

Which AI agents can use phoenix-evals?

Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.

Is phoenix-evals safe to install?

No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.

Who maintains phoenix-evals?

It is published by arize-ai in arize-ai/phoenix. It has 1,649 recorded installs.

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