If you're on a team, a bad agent skill usually gets caught. Someone reviews the PR, someone notices the weird commit message, someone asks "wait, why did it do that." If you're working solo, none of that exists. The skill either works quietly for months or fails quietly for months, and you often can't tell which until something downstream breaks.
That changes how you should evaluate a skill before you let an agent run it unattended. The question isn't "does this look useful" — it's "what happens the first time this hits a case its author didn't think of."
Read the whole file, not the first paragraph
A skill is usually a markdown file with a description and some trigger conditions. Read all of it, including the parts that look like boilerplate. The failure modes live in what the skill doesn't say to do, not in what it does. If a skill describes the happy path in detail and says nothing about what to do when a command fails, an API returns an error, or a file doesn't exist, assume it has no answer — and that the agent will improvise one at the worst possible time.
Check whether it fails loud or fails quiet
This is the single most important property and the one almost nobody checks. Run the skill against an input designed to break it — a missing file, a malformed argument, a network timeout — and watch what happens. A good skill stops and reports the problem. A bad one either crashes in a way that looks like success, or silently falls back to doing something adjacent to what you asked, logged in a way you'd only notice if you were already suspicious.
The MCP ecosystem has produced plenty of real examples of this exact failure recently: tool calls that report "success" when nothing happened, or when something different happened than what was asked. None of that is specific to skills — it's the general failure mode of giving an agent a tool and trusting its own report of what it did. Test for it directly instead of assuming good behavior.
Count the triggers, not the features
A skill with a long feature list but a vague trigger ("use this for code tasks") will fire when you didn't want it to and stay silent when you did. A skill with a narrow, specific trigger ("use when the user asks to refactor a function for readability without changing behavior") competes less with everything else in your setup and is easier to reason about when something goes wrong. If you're assembling your own set of skills, favor fewer, sharply-triggered ones over a large pile of loosely-triggered ones — they interfere with each other less, and when one misfires you have a much smaller list of suspects.
Look for a maintenance signal
Tools and conventions underneath a skill drift — a CLI flag gets renamed, an API shape changes, a file an installer expects moves. A skill with no changelog and no version history gives you no way to tell whether it still matches what's actually installed on your machine. A dated changelog, even a short one, is a signal that someone is tracking drift instead of hoping it doesn't happen. Prefer that over a skill that "looks finished" and hasn't been touched in a year — finished and abandoned look identical from the outside until something breaks.
Check the license before you bill a client against it
This one isn't about reliability, but it bites solo developers specifically because there's no legal review between "skill looked fine" and "invoice sent." Some free skill collections are explicitly non-commercial. If you do any client work at all, confirm commercial use is covered before the skill touches billable work, not after.
None of this requires more than about twenty minutes per skill, and it's twenty minutes you don't get reimbursed for if you skip it and something breaks three weeks later with no team around to notice. We apply exactly this checklist to our own kits before shipping them — the free Agent Starter Kit exists partly so you have something small enough to run this audit against before paying for anything larger (https://agentkitworks.com/answers/best-agent-skills-for-solo-developers).
The checklist works on any skill from anywhere, ours included. The habit that matters is auditing before you trust, not after something goes wrong.
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