Evaluate

evaluate — honest, multi-trial scoring

Turns a candidate into a score you can trust. A reward number is only as honest as the variance around it: agents are stochastic, so the same candidate run twice gives two scores. evaluate's job is to produce a point estimate and the uncertainty that lets the gate decide whether a difference is real. The honesty math lives in cap_evolve.stats; this skill drives the adapter and aggregates.

Inputs / outputs (manifest tokens)

• needs: candidate — a capability variant to score (an id in the run dir or

a directory path).

• provides: scores (the aggregate SplitResult) and traces (per-task

rollouts + feedback — the raw material diagnose turns into a learning signal).

What it produces

A SplitResult containing:

• reward — mean reward across tasks (each task's reward is itself the mean

over its trials). This is the headline point estimate.

• stderr — the combined standard error: between-task variance (do

different tasks agree?) folded together with within-task trial variance (is the agent consistent on a fixed task?). One SE that honestly reflects both sources of noise — not the smaller of the two.

• pass_k — when trials > 1, the estimated probability that all k i.i.d.

trials pass (τ-bench reliability). Optionally pass@k, the probability that at least one of k trials passes (capability). They answer opposite questions; see references/concepts.md.

• per-task scores + feedback — the learning signal diagnose reads.

Dual-mode

This phase runs two ways from the same SKILL.md: standalone as the slash command /cap-evolve:evaluate (the argument-hint shows its run.py args), and orchestrator-callable — cap-evolve run / the orchestrate skill invokes the same scripts/run.py headlessly and threads the run dir between phases.

How to run

python scripts/run.py --run-dir .capevolve/run_XXXX --project .capevolve/project \
    --candidate seed --split val --n-trials 3

--split accepts only train or val — evaluate can never touch test. Test belongs to finalize, which scores it exactly once. Use multiple trials when the target is stochastic: a single trial reports stderr=0, which is a lie that lets the gate accept noise as progress.

Choosing the number of trials

• Deterministic scorer + greedy decode (temp 0): 1 trial is honest.
• Any sampling / temperature / tool nondeterminism: ≥3–4 trials. More trials

shrink stderr ∝ 1/√(trials) and make pass^k / pass@k estimable.

• Trials cost budget linearly. Spend them where variance actually threatens the

decision — usually on the val split the gate reads, not on every probe.

What good vs bad looks like

• Good: n_trials ≥ 3 on a stochastic agent; stderr reported and non-zero;

pass^k present and inspected alongside the mean.

• Bad: single-trial scores on a stochastic agent feeding a significance gate

(every marginal "win" is noise); reading the test split "just to check"; trusting a high mean when pass^k is low (the gain is fragile across trials).

References

• references/concepts.md — variance decomposition, combined standard error,

pass^k vs pass@k with their unbiased estimators, multi-trial budgeting, and bootstrap CIs, with sources.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: skillberry-ai
• Source: skillberry-ai/cap-evolve
• License: Apache-2.0

Install and usage instructions live in the source repository linked above.