Skill vs Tool
A skill is instructions — it tells an agent how to approach a task well. A tool is a function the agent can call — it actually does something: search, read a file, run code. A skill doesn't replace tools; a skill's instructions typically tell the agent which tools to use, and when, for the task the skill covers.
What a skill is
A packaged set of instructions for one kind of task, kept out of the agent's prompt until that task actually comes up. Loading every skill's full instructions all the time would defeat the purpose, so the agent sees only a short description up front and loads the full instructions only once a task matches. Learn more: Agent Skills.
What a tool is
A specific action the model can request, with arguments, that the application actually carries out — the model never runs anything itself, it returns a structured request and the code behind it executes. Learn more: Tool Calling.
Side by side
| Skill | Tool | |
|---|---|---|
| What it is | Instructions | A function the agent can call |
| What it does | Tells the agent how to approach a task | Actually does something — search, read a file, run code |
| Relationship | Often calls several tools along the way | Doesn't replace skills; skills call tools, not the other way around |
| Loaded when | A matching task comes up | The model decides this specific action is needed |
Why the confusion happens
Both exist to keep something out of the agent's main context until it's actually needed, which makes them feel like the same kind of thing from a distance. What's different is what each one actually contains: a tool is executable — calling it does something in the real world. A skill is instructional — loading it just changes what the agent knows about how to approach the task, and it still needs real tools to act on any of it.
Reviewing a pull request, with both
A skill for "reviewing a pull request well" might contain instructions on what to check, in what order, and what tone to use in comments — but it still calls ordinary tools to actually fetch the diff, read the files, and post the comment. The skill is the judgment; the tools are what carry it out.
In this guide
FAQ
Can a skill work with no tools at all?
Only for a task that's purely about how the agent reasons or writes, with nothing that needs a real action — otherwise a skill's instructions are only useful if the agent still has tools available to actually carry out what the skill tells it to do.