eval-loop-for-agents

Builds an eval harness that scores agent runs across prompt, model, and tool changes.

1|Updated Jul 3, 2026
One-click install
npx skills add https://github.com/Nandansai08/skillz --skill eval-loop-for-agents-nandansai08
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: eval-loop-for-agents
Source: https://github.com/Nandansai08/skillz/tree/main/skills/loop-engineering/eval-loop-for-agents
Command: npx skills add https://github.com/Nandansai08/skillz --skill eval-loop-for-agents-nandansai08

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve? Agent changes ship blind: every prompt tweak, model upgrade, or tool swap is a bet with no scoreboard, and nondeterministic runs make single-run spot checks meaningless. This Skill builds a repeatable eval harness so agent changes ship with measured evidence instead of vibes. ## Core Features & Use Cases - Task Set Construction: Harvests real production tasks, pinned past failures, and synthetic edge cases into a version-controlled suite with success criteria and category tags. - Variance-Aware Scoring: Runs each task multiple times, reports pass rates with run counts, and establishes per-task variance bands so noise is never mistaken for regression. - Judge Calibration & Regression Gating: Calibrates LLM judges against human labels, freezes baselines with config fingerprints, and gates changes on per-category deltas wired into CI. - Use Case: Migrating a ticket-triage agent to a new model, the suite reveals the aggregate score improved while the hardest ticket category regressed 23 points — invisible without category-level readouts. ## Quick Start Build an eval harness for my agent that runs a versioned task set multiple times, scores results with checkable criteria and a calibrated judge, and gates prompt or model changes on per-category regression deltas.

Frequently Asked Questions about eval-loop-for-agents

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I test whether a prompt change made my agent worse?▼

Run the agent against a versioned task set of 20-50 tasks before and after the change, with multiple runs per task. Compare per-category pass rates against baseline variance bands rather than trusting a single aggregate score.

How many times should I run each agent eval task?▼

Run 3 times for tasks with pass rates near 0% or 100%, and 5-10 times for decision-relevant tasks gating a ship call. Always report pass rates with run counts, since single runs of nondeterministic agents measure luck.

How do I evaluate an agent when outputs are subjective?▼

Score with a checkable-first hierarchy: binary completion checks, then thresholds on cost and iterations, then a rubric-based LLM judge for the remainder. Calibrate the judge against human labels on a 30-60 sample and require roughly 80% agreement before trusting it.

Should the judge model be the same model the agent uses?▼

No. A judge sharing the agent's model introduces self-preference bias that inflates exactly the comparisons you care about. Use a different model family for the judge and re-calibrate whenever the judge model changes.

When is a full agent eval harness not worth building?▼

Skip it for debugging a single failed run, which needs trace-level diagnosis instead, and for deterministic prompt templates where snapshot tests suffice. The harness earns its cost when loops and tools make runs nondeterministic.