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Writing the Agent’s prompt is the single biggest lever on how it feels to talk to. The full guide lives with the rest of the Agent-building material.

Personality Design

The complete guide: the golden rule, what never to write, how natural speech actually sounds, response length, the four pillars of a believable character, emotional calibration, and a full prompt template.
The rules that matter most, in short:
  • Write speech, not prose. No stage directions, no markdown, no emoji, nothing a voice cannot say out loud.
  • Keep replies short. Voice is serial, and a listener cannot skim.
  • Give the character a perspective, not just information.
  • Stay in one emotional register. A character that swings tone stops feeling like a person.

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See also