Record an explicit reasoning step — a plan, a hypothesis, a trade-off analysis, or a checkpoint before an irreversible or multi-tool action. It obtains no new information, reads or changes nothing, and runs nothing; it only appends your thought to the log.

**When to use:**
- Before a destructive, hard-to-reverse, or multi-step tool sequence, to lay out the plan and the checks first.
- When several pieces of evidence must be reconciled before deciding (e.g. conflicting logs, an ambiguous root cause).
- To checkpoint intermediate conclusions on a long task so they survive later steps.

**When NOT to use:**
- For routine, obvious next actions — just take them. A think step that only restates the task wastes a turn.
- As a substitute for acting: if the next move is clear, call the real tool instead of narrating intent.
