Skills and subagents solve different agent problems

A skill packages reusable instructions for an agent; a subagent performs a delegated piece of work with its own task context. Choose based on whether you need repeatable guidance or a separable unit of investigation or implementation.

Use a skill for repeatable guidance

A skill packages instructions or resources that an agent can apply when a task calls for them. A subagent is a separate agent run delegated a defined piece of work. One changes what the current agent knows how to do; the other changes who performs a portion of the task and what context that worker receives.

Delegate a bounded work unit

Use a skill when the procedure is reused, belongs with the main task, and needs consistent guidance. Keep the skill focused: state when it applies, required inputs, the steps to follow and how to recognize a finished result. A narrow skill is easier to maintain than a long instruction file that applies to every request.

Write a useful handoff

Delegate to a subagent when the work is separable, can be described with a clear output, or can proceed in parallel. Give it the relevant files, constraints and acceptance criteria. Ask for findings or a patch that can be independently reviewed. Delegation has coordination cost, and context omitted from the handoff may lead to a plausible but wrong result.

Combine both when it helps

The two patterns can work together: a subagent may use the same relevant skill, while the main agent integrates the result. Avoid delegation when the task is tiny, tightly coupled to changing decisions, or requires access the worker should not have. Limit tools and permissions to the task.

Account for coordination costs

For a concrete choice, ask whether the missing capability is repeatable guidance or an independent unit of work. Guidance belongs in a skill; an independent investigation or implementation may suit a subagent. Product-specific behavior differs, so follow the current documentation for the agent system you use.

Official reference

Consult the official documentation for current instructions and applicable terms.