Most prompt engineering advice tells you to write longer, more detailed prompts. But some of the biggest improvements come from a single word or short phrase that changes how Claude approaches a task entirely.
These aren't tricks — they're legitimate instructions that activate specific behaviors Claude is capable of but doesn't default to. Here are the ten most useful, each with a before and after example.
1. ultrathink
Adding "ultrathink" to any prompt triggers Claude's extended reasoning mode. Instead of producing the first plausible answer, it reasons through the problem more carefully before responding. Use this for decisions, analysis, and anything where you want Claude to show its work rather than just produce a quick output.
Before: "What's the best pricing strategy for a new SaaS product?"
After: "ultrathink — what's the best pricing strategy for a new SaaS product targeting mid-market HR teams?"
The difference in depth and nuance is immediately obvious.
Words 2 through 6 are the ones most users find transformative. They specifically override the default behaviors that make AI output feel sanitized, hedged, and generic. Word 3 in particular — which most people have never heard of — is the one professional writers use to make Claude match an existing voice rather than its own default tone.
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