Write guidance the agent can apply
A useful skill names the kind of request it covers, the steps to follow, and the output expected. Include required terminology and sources, but avoid long background that does not change how the task is done. Clear, bounded instructions are easier to apply consistently than a general document that tries to cover every situation.
Treat reusable guidance as part of the agent's behavior. If it names tools, files, or permissions, make sure those are available to the agent and appropriate for its work. Do not put passwords or private customer data in the instructions; provide sensitive values through the approved secure settings when needed.
Keep instructions current and test them
Review a skill after the process, product, or policy changes. Outdated steps can make otherwise good agent work unreliable. Ask the agent to use the guidance on a representative example and inspect whether it followed the intended sequence and produced the requested format.
If the result goes wrong, revise the specific instruction that caused confusion instead of adding broad warnings everywhere. Keep task-specific guidance separate from general rules so a specialized procedure does not affect unrelated requests.