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Phoenix Evals

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Build and validate evaluators for AI applications.

by github37.7k stars on github/awesome-copilot
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Updated Aug 10, 2026
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Free · Opens the source repo

What Phoenix Evals does

Phoenix Evals is designed for developers and data scientists who want to create and validate evaluators for AI and LLM applications. The skill emphasizes a code-first approach, enabling users to build evaluators that can assess the performance and accuracy of AI models. By integrating human validation into the evaluation process, Phoenix Evals ensures that the evaluators are not only automated but also reliable.

The skill provides a structured workflow that guides users through the process of setting up their environment, selecting evaluation criteria, and building both code and LLM evaluators. It includes comprehensive references for Python and TypeScript, making it versatile for different programming environments. Users can choose from pre-built evaluators or create custom ones tailored to their specific needs, enhancing the flexibility of the evaluation process.

In addition to building evaluators, Phoenix Evals offers tools for error analysis and validation. Users can analyze errors through detailed tracing and sampling, categorize failures, and validate the accuracy of their evaluators against human labels. This focus on validation helps ensure that the evaluators are effective and can be trusted in production environments.

Overall, Phoenix Evals is a valuable resource for anyone involved in developing AI applications, providing the necessary tools and references to build robust evaluators that meet industry standards.

When to use it

Use Phoenix Evals when you need to create evaluators for AI models and want to ensure they are validated against human standards.

When not to use it

This skill may not be suitable for those looking for a fully automated evaluation solution without any human oversight or validation.

What you can build with it

Setting Up an Evaluator

Begin with the setup guides for Python or TypeScript, then follow the workflow to build your first evaluator.

Running Experiments

Use the experiments section to create datasets and run evaluations, helping you fine-tune your AI models.

Error Analysis

Implement error analysis techniques to identify and categorize failures in your AI applications, improving overall performance.

How to install Phoenix Evals

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1. Install with the skills CLI

npx skills add github/awesome-copilot/phoenix-evals --agent claude-code

2. Or install it manually

Download the skill folder and drop it into ~/.claude/skills/ for all projects, or .claude/skills/ to scope it to one repo. Restart Claude Code so it picks up the new skill.

Anthropic's agentic coding CLI, and the reference implementation of Agent Skills. Drop a skill folder into ~/.claude/skills and Claude Code loads it automatically whenever a task matches the skill's description. Claude Code docs

Inside SKILL.md

Written by github

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
Understand experimentsexperiments-overview
Run experimentexperiments-running-python, experiments-running-typescript
Create datasetexperiments-datasets-python, experiments-datasets-typescript
Generate synthetic dataexperiments-synthetic-python, experiments-synthetic-typescript
Validate evaluator accuracyvalidation, validation-evaluators-python, validation-evaluators-typescript
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-setuperror-analysisaxial-codingevaluators-overview

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

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

Production: production-overviewproduction-guardrailsproduction-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
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% TPR/TNR
Binary > LikertPass/fail, not 1-5

Frequently asked questions about Phoenix Evals

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