Skills
So far, you have an agent with a system prompt, tools, and a way to reach it. That is already powerful. Now we look at a concept that lets you upgrade what you have — making the agent’s instructions sharper and more focused.
On-demand instructions
Section titled “On-demand instructions”A skill is a set of instructions that the agent loads only when it needs them.
Think of the system prompt as the agent’s general knowledge — always present, always shaping its behavior. A skill, by contrast, is specialist knowledge that the agent pulls in for a specific task.
A skill is simple: it has a title, a description, and content — the actual instructions. The agent loads a skill by calling a tool. The skill’s instructions are returned as the tool response and become part of the agent’s context from that point forward.
Why skills matter
Section titled “Why skills matter”Without skills, you would have to put every instruction into the system prompt. That means the agent would carry instructions for every system it might use, every workflow it might follow — all the time, whether it needs them or not.
Skills solve this. Each skill captures the instructions for one specific aspect of the agent’s work. The agent loads the right skill at the right time.
Example: a Todoist skill
Section titled “Example: a Todoist skill”In the Tools section, we showed an agent using the Todoist API with just a secret and command execution. That works — but the agent has to figure out the API details every time.
A Todoist skill would contain instructions like:
Todoist
Use the Todoist REST API v2 at
https://api.todoist.com/rest/v2. Authenticate with the Bearer token from theTODOIST_API_KEYsecret. To get today’s tasks, use the/tasksendpoint with thefilterparameter set totoday. To complete a task, send a POST to/tasks/{id}/close.
With this skill loaded, the agent does not need to figure out the API from scratch. It has clear, reliable instructions — making it faster and more consistent.
Skills are not limited to system access. You can create skills for common workflows, recurring processes, communication styles, or any other aspect of the agent’s work that benefits from clear, reusable instructions. Over time, your library of skills becomes a knowledge base that makes every agent more capable.
For a deeper look at how to design skills well — how to write titles that make the agent reach for the right skill at the right time, and how to decide what belongs in a skill versus in the system prompt — see the Agent Design Guide.