Topic instructions versus action logic for strict business rules
Key Takeaway
Use instructions for guidance, and use deterministic logic for any rule that must always hold.
Agent instructions are natural-language guidance, so they can't guarantee that the agent follows a business rule every time. Rules that must always hold, such as refund eligibility, belong in deterministic logic instead: the flow or Apex class behind an agent action, logic in Agent Script, or filters that hide an action until conditions are met.
What a subagent contains
Beginning in April 2026, agent topics are called subagents, with no change in functionality. A subagent contains instructions, which guide how the agent makes decisions, and actions, which are the tools for the job.