Custom topic scope and instructions
Key Takeaway
By default, a subagent's name and description decide which requests reach it. Its reasoning instructions decide how the agent handles those requests. To run an action deterministically before the LLM reasons, put the action in the reasoning instructions instead of the reasoning actions.
A custom subagent (called a topic before April 2026) is a job you define for an Agentforce agent. Its name and description set its scope, which means the user requests that should be sent to it. Its reasoning instructions tell the agent how to handle those requests after they arrive. When both are written well, the agent is more likely to pick the right job and behave consistently.
What a subagent is
Beginning in April 2026, agent topics are called subagents. The functionality didn't change. During the transition, you may see both terms for the same thing.
A subagent is a particular job an agent can do. The full set of subagents assigned to an agent defines what the agent can handle. Each subagent has these parts:
- Name
- Description
- Reasoning instructions
- Reasoning actions
- Action definitions