A developer configures AgentDefinitions for search and synthesis subagents and writes a coordinator prompt describing when to delegate to each. In testing, the coordinator describes the delegation it intends but never actually spawns a subagent. What is the most likely cause?

Answer: D — The coordinator's allowedTools list doesn't include "Task", which is the tool that spawns subagents

Subagents are spawned through the Task tool, so the coordinator's allowedTools must include "Task". Without it, the coordinator can only talk about delegating. Short descriptions (a) affect which subagent is chosen, not whether any can be spawned; subagent prompts (b) never run if nothing is spawned; and goal-based prompts (c) are the recommended style.