When a skill's rules fight your own
A skill is a set of instructions written for the author's own setup. Drop it into yours and some of those instructions will contradict rules you already gave Claude. Neither file mentions the other, so the session picks one, and you find out which one later. These are the clashes I hit while reading and test-running skills in November 2026, and what I check now before installing one.
Where they collide
Where output goes. shadcn/improve writes its plans to a plans/ folder. My own rules say plans go into a plan tracker, never a markdown file. The two instructions can't both hold, so a session has to break one of them. The skill itself is good; I would adopt it with its output redirected.
Git rules. The AGENTS.md in ivankovic/omnidiff says "Do not commit to main". In my repo a scheduled job commits its daily output to main, so the rule would either block that job or push every session onto a branch the job then bypasses. The same file says its log file "is git-ignored", which is true in its own repo and false in mine. A session following it would leave an untracked file behind.
Look and style. The landing-page skill in elayadesign/ai-design-skills ships a strict visual system (type, spacing, radius, backgrounds, motion) that overrides framework defaults. If you already have a design system, the two will fight on every page. I would skip it, or read it only for ideas.
Who keeps the to-do list. claude-mem's session-start text tells Claude to keep all to-do lists in claude-mem "instead of any built-in to-do tool". A plugin can inject instructions like that at the start of every session, which makes the clash easy to miss.
Response style. ayghri/i-have-adhd sets ten rules for how answers look. One of them conflicted with a line in my rules file, and the skill says nothing about which should win.
Overlap is a quieter version of the same problem
Two skills that cover the same job split the trigger. Several of the skill packs I read overlapped with design, video or research skills I already had. NVIDIA/SkillEvaluator has an overlap check that compares every skill in a folder by embeddings. I have not run it: it wasn't installed on my machine and I had no NVIDIA API key set. So treat it as a lead, not a result.
What I check before installing a skill
- Search the skill's files for every path it writes to, and every git command or branch rule it gives.
- Search for "instead of", "always" and "never". Those are the lines that override something.
- Search for anything a hook injects at session start. That text runs before your own prompt.
- If a line contradicts your rules, decide which wins and write that decision into your rules file. Don't leave it to the session.
- If the skill duplicates one you have, compare the two on the same input and keep one.
A quick way to do steps 1 and 2 before you install anything:
grep -rn -i -E "instead of|always|never|commit|branch|plans/" path/to/skill/