What it is. A skill is a self-contained bundle — a prompt or a folder with a SKILL.md and optional scripts — that describes when it applies and how to do the task. When the assistant hits a matching situation, it loads the skill's instructions into context. Skills are how you extend an assistant like Claude with specialized behavior (writing SQL migrations, generating a report, running a linter) without hard-coding it into the base prompt.
Skill versus tool. A tool is a function the AI can call at any moment. A skill is a chunk of expertise — instructions, examples, sometimes a script — that the AI loads only when relevant. Think of tools as verbs and skills as playbooks.
What to check. A skill runs with whatever permissions the host gives it. If its SKILL.md tells the AI to run shell commands or write files, those calls go through the assistant's normal permission gates. AgentMaps flags each skill's shell, write, and token requirements up front so you can decide before you install.