Prompt Engineer Toolkit

Overview

Use this skill to move prompts from ad-hoc drafts to production assets with repeatable testing, versioning, and regression safety. It emphasizes measurable quality over intuition. Apply it when launching a new LLM feature that needs reliable outputs, when prompt quality degrades after model or instruction changes, when multiple team members edit prompts and need history/diffs, when you need evidence-based prompt choice for production rollout, or when you want consistent prompt governance across environments.

Core Capabilities

• A/B prompt evaluation against structured test cases
• Quantitative scoring for adherence, relevance, and safety checks
• Prompt version tracking with immutable history and changelog
• Prompt diffs to review behavior-impacting edits
• Reusable prompt templates and selection guidance
• Regression-friendly workflows for model/prompt updates

Key Workflows

1. Run Prompt A/B Test

Prepare JSON test cases and run:

python3 scripts/prompt_tester.py \
  --prompt-a-file prompts/a.txt \
  --prompt-b-file prompts/b.txt \
  --cases-file testcases.json \
  --runner-cmd 'my-llm-cli --prompt {prompt} --input {input}' \
  --format text

Input can also come from stdin/--input JSON payload.

2. Choose Winner With Evidence

The tester scores outputs per case and aggregates:

• expected content coverage
• forbidden content violations
• regex/format compliance
• output length sanity

Use the higher-scoring prompt as candidate baseline, then run regression suite.

3. Version Prompts

# Add version
python3 scripts/prompt_versioner.py add \
  --name support_classifier \
  --prompt-file prompts/support_v3.txt \
  --author alice

Diff versions
python3 scripts/prompt_versioner.py diff --name support_classifier --from-version 2 --to-version 3

Changelog
python3 scripts/prompt_versioner.py changelog --name support_classifier

4. Regression Loop

• Store baseline version.
• Propose prompt edits.
• Re-run A/B test.
• Promote only if score and safety constraints improve.

Script Interfaces

• python3 scripts/prompt_tester.py --help

- Reads prompts/cases from stdin or --input

- Optional external runner command

- Emits text or JSON metrics

• python3 scripts/prompt_versioner.py --help

- Manages prompt history (add, list, diff, changelog)

- Stores metadata and content snapshots locally

Pitfalls, Best Practices & Review Checklist

Avoid these mistakes:

• Picking prompts from single-case outputs — use a realistic, edge-case-rich test suite.
• Changing prompt and model simultaneously — always isolate variables.
• Missing must_not_contain (forbidden-content) checks in evaluation criteria.
• Editing prompts without version metadata, author, or change rationale.
• Skipping semantic diffs before deploying a new prompt version.
• Optimizing one benchmark while harming edge cases — track the full suite.
• Model swap without rerunning the baseline A/B suite.

Before promoting any prompt, confirm:

• [ ] Task intent is explicit and unambiguous.
• [ ] Output schema/format is explicit.
• [ ] Safety and exclusion constraints are explicit.
• [ ] No contradictory instructions.
• [ ] No unnecessary verbosity tokens.
• [ ] A/B score improves and violation count stays at zero.

References

• references/prompt-templates.md
• references/technique-guide.md
• references/evaluation-rubric.md
• README.md

Evaluation Design

Each test case should define:

• input: realistic production-like input
• expected_contains: required markers/content
• forbidden_contains: disallowed phrases or unsafe content
• expected_regex: required structural patterns

This enables deterministic grading across prompt variants.

Versioning Policy

• Use semantic prompt identifiers per feature (support_classifier, ad_copy_shortform).
• Record author + change note for every revision.
• Never overwrite historical versions.
• Diff before promoting a new prompt to production.

Rollout Strategy

• Create baseline prompt version.
• Propose candidate prompt.
• Run A/B suite against same cases.
• Promote only if winner improves average and keeps violation count at zero.
• Track post-release feedback and feed new failure cases back into test suite.