The d4-rich Prompt Pattern#

Non-reasoning chat models (deepseek-V4-Flash, grok-4.3, kimi with thinking disabled) collapse on multi-file refactor tasks when given thin or baseline prompts. Pass rates of 0-33% on canaries that reasoning models clear at 67-100%. The cheap fix is a three-part prompt addendum: completion checklist, callsites-exhaustively-updated rule, and verify-before-push instruction. Drop it into the system prompt of a non-reasoning model and the canaries go green. Drop it into a reasoning model and you pay 12× more for 0% quality improvement.

Tool Use Patterns#

An agent with access to 30 tools is not automatically more capable than one with 5. What matters is how it selects, sequences, and validates tool use. Poor tool use wastes tokens, introduces latency, and produces wrong results that look right.

Choosing the Right Tool#

When multiple tools could handle a task, the agent must pick the best one. This is harder than it sounds because tool descriptions are imperfect and tasks are ambiguous.