Skill
Agent Skills are a technical feature in Claude that enable AI agents to perform specific, well-defined tasks by leveraging structured function definitions. Skills function as a bridge between an agent’s reasoning capabilities and external systems or computational operations, allowing Claude to understand what actions are available and when to invoke them appropriately.
Implementation
Skills are implemented through function calling, a mechanism that lets Claude recognize when a task requires external action and specify which skill to use along with the necessary parameters. When an agent encounters a problem it cannot solve through reasoning alone, it can request the execution of a skill by providing a structured function call that includes the skill name and required inputs. The agent harness then executes this function and returns the results to Claude, creating a feedback loop that informs subsequent reasoning steps.
Design and Usage
Effective skills are built on clear, descriptive function definitions that specify what the skill does, what parameters it requires, and what output it produces. This structured information enables Claude to make informed decisions about when and how to use available skills. By explicitly defining capabilities through skills, developers can guide agent behavior, constrain available actions to appropriate domains, and ensure that external operations are called with valid inputs. This approach allows agents to handle complex, multi-step tasks that combine reasoning with practical execution.