What is an agent skill?

An agent skill is instructions, not code. It is a document describing how to approach a particular kind of task: which tool to reach for, in what order, what the common failure modes are, and what a correct result looks like. The agent loads it when the task matches and ignores it otherwise.

The distinction from a tool is worth holding on to. A tool gives an agent a new capability. A skill teaches it to use the capabilities it already has properly.

Why instructions need packaging at all

A model handed a scraping tool will use it, and will use it badly in predictable ways: rendering every page whether or not it needs to, requesting a URL list one call at a time instead of in a batch, treating a challenge page as content, retrying an identical failing request. None of these are model failures exactly. They are things a practitioner knows and a model has no reason to.

Putting that knowledge in the system prompt does not scale, because the prompt is finite and most of it would be irrelevant to any given task. A skill is loaded only when relevant, which is why the pattern exists.

What a skill usually contains

• When it applies. The trigger, so the agent knows whether to read further.
• The approach. The sequence that works, including what to try first and when to escalate.
• Known failure modes. What a block page looks like, what a soft failure looks like, what to do about each.
• Verification. How to tell the result is right rather than merely present.

The good ones are short and opinionated. A skill that lists every option without saying which to pick has moved the decision back to the model.

Where Zenrows fits

Zenrows ships skills with its CLI, installable and manageable from the command line. They cover the decisions above: which primitive fits the task, when rendering is worth its cost, how to recognise a block, how to batch a URL list rather than looping.

They sit inside the wider Agent Toolkit, alongside the MCP server, templates, workflows, recipes and evals. The toolkit's stated purpose is making Zenrows installable and usable by an agent rather than only callable by one, and skills are the part that carries the judgement.