Menu

Individual skill

eval-driven-dev

Improve AI application with evaluation-driven development. Define eval criteria, instrument the application, build golden datasets, observe and evaluate application runs, analyze results, and produce a concrete action plan for improvements. ALWAYS USE THIS SKILL when the user asks to set up QA, add tests, add evals, evaluate, benchmark, fix wrong behaviors, improve quality, or do quality assurance for any Python project that calls an LLM model.

skills/eval-driven-dev/SKILL.md

Read pinned source

Source commit edbecfa9099c4addae1f500cca1ac067204b30fd

What was checked

Matches the observed repository HEAD
Yes
Scanner rules are current
Yes
Repository scan complete
No
Skill scan complete
No
Observed behavior
Network or broad shell
Last checked
Nov 4, 2026

These are observations at the recorded commit, not a guarantee of safety. Review the source before running it.

Install this skill

Choose an agent in your Stack or copy a command below. Commands fetch the pinned commit and copy only this skill directory. Existing destinations are refused. Copying a command does not install anything.

An install command is unavailable: current rules, complete repository and skill scans, an eligible behavior level and a permitted license are required.

Repository context

Repository stars (not skill ratings)
40,891
Repository last updated
Nov 6, 2026
License
MIT

Observed agent integration: No specific integration evidence. Standard SKILL.md installation does not imply verified compatibility.

Files and excerpt

File metadata and permitted, redacted excerpts come from the recorded scan. Source links are pinned to that commit.

Browse files
Read excerpt

# Eval-Driven Development for Python LLM Applications

You're building an **automated evaluation pipeline** that tests a Python-based AI application end-to-end — running it the same way a real user would, with real inputs — then scoring the outputs using evaluators and producing pass/fail results via `pixie test`.

**What you're testing is the app itself** — its request handling, context assembly (how it gathers data, builds prompts, manages conversation state), routing, and response formatting. The app uses an LLM, which makes outputs non-deterministic — that's why you use evaluators (LLM-as-judge, similarity scores) instead of `assertEqual` — but the thing under test is the app's code, not the LLM.

During evaluation, the app's own code runs for real — routing, prompt assembly, LLM calls, response formatting — nothing is mocked or stubbed. But the data the app reads from external sources (databases, caches, third-party APIs, voice streams) is replaced with test-specified values via instrumentations. This means each test case controls exactly what data the app sees, while still exercising the full application code path.

**Rule: The app's LLM calls must go to a real LLM.** Do not replace, mock, stub, or intercept the LLM with a fake implementation. The LLM is the core value-generating component — replacing it makes the eval tautological (you control both inputs and outputs, so scores are meaningless). If the project's test suite contains LLM mocking patterns, those are for the project's own unit tests — do NOT adopt them for the eval Runnable.

**The deliverable is a working `pixie test` run with real scores** — not a plan, not just instrumentation, not just a dataset.

This skill is about doing the work, not describing it. Read code, edit files, run commands, produce a working pipeline.