agentmods.dev

CustomerNewsletter: Skill for Claude Code

.github/skills/testing-prompt-changes/SKILL.md

testing-prompt-changes is a skill for Claude Code, Codex from briancl2/CustomerNewsletter. It costs 60 tokens per session (1,634 once invoked), scanned A, original, MIT.

A testing process for changes to prompts, skills, or agent instructions that uses repeated hypothesis, implementation, grading, and rework cycles. It compares results with known-good benchmark outputs.

In plain words
What is it for?
Use it when changing newsletter prompts, skills, agent definitions, or related instructions, then record the results in workspace/higr_log.md.
Why use it?
It makes output-quality changes testable and records whether each expected improvement actually worked.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

This is briancl2/CustomerNewsletter's own configuration. It tells Claude Code and Codex how to work on CustomerNewsletter itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything CustomerNewsletter configures →

not rated 11repo 5mo ago A scan 60 tokens original MIT
View source ↗ briancl2/CustomerNewsletter briancl2.github.io
Reuse

Borrowing it

Nothing to install: this file belongs to briancl2/CustomerNewsletter. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/briancl2/CustomerNewsletter/main/.github/skills/testing-prompt-changes/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/briancl2/CustomerNewsletter

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for testing-prompt-changes

README.md
[![agentmods](https://agentmods.dev/badge/skills/briancl2/customernewsletter/testing-prompt-changes/github.svg)](https://agentmods.dev/skills/briancl2/customernewsletter/testing-prompt-changes)
Your own site
<a href="https://agentmods.dev/skills/briancl2/customernewsletter/testing-prompt-changes"><img src="https://agentmods.dev/badge/skills/briancl2/customernewsletter/testing-prompt-changes/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for testing-prompt-changes

Your own site · 80×15
<a href="https://agentmods.dev/skills/briancl2/customernewsletter/testing-prompt-changes"><img src="https://agentmods.dev/badge/skills/briancl2/customernewsletter/testing-prompt-changes.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 60 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,634 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00060 $0.01634
Opus 5.5 $0.00024 $0.00654
Sonnet 5.5 $0.00012 $0.00327
Haiku 4.5 $0.00006 $0.00163

Measured 2mo ago against content hash 1211305eec34, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

testing-prompt-changes scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.github/skills/testing-prompt-changes/SKILL.md · 173 lines

How it starts

The opening of the file, as written. The whole thing — 173 lines — stays where its author put it; the contents beside it link to each section on GitHub.

HIGR Prompt Testing

Test prompt and skill changes systematically with Hypothesis-Implement-Grade-Rework cycles. Every modification requires testable predictions and evidence-based grading against benchmark data.

Quick Start

  1. Write testable hypotheses before editing any prompt or skill
  2. Implement the change (delete superseded content)
  3. Run against benchmark inputs, compare to known-good output
  4. Grade each hypothesis: Good / Bad / Ugly
  5. Rework if needed; record results in workspace/higr_log.md

When to Use

  • Modifying phase prompts (.github/prompts/phase_*.prompt.md)
  • Updating skill SKILL.md or references/
  • Changing agent definition (.github/agents/customer_newsletter.agent.md)
  • Changing copilot-instructions.md
  • Any change that affects newsletter output quality

HIGR Cycle

flowchart LR
    H[Hypothesis] --> I[Implement]
    I --> G[Grade]
    G --> R{Rework?}
    R -->|Bad/Ugly| H
    R -->|Good| D[Done]

Step 1: Hypothesis (Pre-Implementation)

Before editing any prompt or skill, write testable predictions:

Hypothesis ID Change Expected Effect Testable Criteria
H1 [specific change] [expected output difference] [how to verify]

Hypothesis Requirements:

  • Specific — Not "newsletter will be better"
  • Observable — Can see the difference in output
  • Falsifiable — Possible to determine if wrong

Example Good Hypotheses:

ID Change Expected Effect Criteria
H1 Add SOURCES.yaml reading to url-manifest URL count increases, covers all kb/ sources URL count within 20% of benchmark, 0 false URLs
H2 Extract selection criteria to skill reference Curation quality matches Dec 2025 benchmark ≥70% item overlap with benchmark curated sections
H3 Add IDE parity grouping to content-format-spec IDE updates grouped correctly VS Code/Visual Studio/JetBrains in single section

Read the full file on GitHub · 173 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2mo ago First seen · 173 lines · 60 tokens per session scan A 1211305eec34

Subscribe to this mod's changes

testing-prompt-changes is a skill published in the GitHub repository briancl2/CustomerNewsletter (11 stars, last pushed 5mo ago), licensed MIT. It adds 60 tokens to every session and 1,634 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Data and AIPromptingTestingagentic-workflowsagentscopilotllmopsmkdocsnewsletter
Related

testing-prompt-changes compared with skills from other repositories

testing-prompt-changes next to 6 skills from other repositories
ModTypeStarsLast pushLicenceScanTokensWorks with
testing-prompt-changesbriancl2/CustomerNewsletterSkill115mo agoMITA60Claude Code, Codex
deepevalsammcj/agentic-codingSkill1682d agoApache-2.0A19Claude Code, Codex
prompt-enhancersammcj/agentic-codingSkill1682d agoApache-2.0A63Claude Code, Codex
ambitious-model-usesammcj/agentic-codingSkill1682d agoApache-2.0A58Claude Code
llm-prompting-guidesammcj/agentic-codingSkill1682d agoApache-2.0A79Claude Code, Codex
promptbeat-run-quick-evaltophant-ai/aibeatSkill1.4k16d agononeA46Claude Code, Codex
hatch3r-ai-featurehatch3r/hatch3rSkill261mo agoMITA39Claude Code