Open-source skill audit tool gains traction for cleaning up Fable 5.1 prompts

From Sept 2-3, an open-source tool for auditing Claude skills gained traction among developers, with several authors sharing experiences and tips for pruning.

Confirmed

• The tool was built and open-sourced by Lance Martin (@RLanceMartin); usage is running /claude-api prompt-audit while trying Fable 5.1 to audit all Skills in a workspace.
• What it does: finds large amounts of redundancy and duplicate constraints in skill configs, flags rules unnecessary for the latest model, and detects dead slash commands and hardcoded content.
• One user switching from Claude Code to Fable 5.1 reported that emphasis words in old prompts triggered redundant tool calls, recommending a prompt-audit pass right after switching to a new model.
• Lance Martin said he is applying the audit to all of his own skills.
• Peter Yang (@petergyang) shared that the tool not only optimizes for the latest model but also found redundancy and contradictory rules in his existing skills; he recommends every developer run it at least once.
• Peter Yang also advised installing fewer AI Skills—keeping only a few frequently used, short ones—and periodically deleting unused ones.

Why it matters

• As models improve, rules added earlier to constrain behavior may become redundant or even conflicting, and emphasis words in old prompts can cause redundant tool calls on new models; regular audits keep configs clean and cut maintenance cost.
• By auditing skills with a skill, the tool offers an open-source, reusable automation path that the community received positively.

2026-09-02 ~ 2026-09-03 · 6 related posts

Full story(2 episodes)→

• Episode 1: Anthropic Releases Official Prompting Guide for Claude Fable 5.1(2026-09-02, 9 posts)
• Episode 2: Open-source skill audit tool gains traction for cleaning up Fable 5.1 prompts(2026-09-02, 6 posts)

• Fable 5.1 Tip: Run prompt-audit to clean up skill redundancies — petergyang · 2026-09-02
• Expert advises pruning AI Skills and using Claude to audit redundancies — petergyang · 2026-09-02
• [source] Anthropic Recommends Running Prompt Audit for Fable 5.1 Optimization — RLanceMartin · 2026-09-02
• [source] Skill-auditing Skill Finds Redundancies in Your Claude Skills; Devs Urge Trimming to a Dozen — petergyang · 2026-09-03
• Audit your agent skills for Fable 5.1 with /claude-api prompt-audit to prune stale rules — xiaohu · 2026-09-03
• [source] Switching to Fable 5.1? Run a Prompt Audit First — Old Emphasis Triggers Wasted Tool Calls — RLanceMartin · 2026-09-03