You can shape how the assistant writes in two places:
  • The knowledge base’s persona — the default voice for every surface that uses that knowledge base.
  • Customizations — reusable voices you assign to one widget, bot or form. Use them when a public docs widget and an internal bot on the same knowledge base should sound different.
Neither can add facts. They change how answers are written, not what the assistant knows.

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Knowledge base persona

Open the knowledge base, go to Settings → AI Persona & Instructions, and fill in:
SettingWhat it does
Persona PromptWho the assistant is, in a sentence or two. Example: You are Aria, a support assistant for Acme Corp.
Response ToneDefault, Friendly, Formal or Technical
Custom InstructionsRules for every answer, such as Recommend support@acme.com for billing questions.
This voice is used by the Playground, Ask, the API, MCP, and any widget, bot or form that has no customization assigned.

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Customizations

1

Create one

Go to Customizations in the sidebar and click New customization.
2

Fill in the fields

See the table below. Every field except Name is optional.
3

Assign it

Open a widget, bot, form deflector, helpdesk integration or agent app and pick it under Voice. Knowledge base’s own persona means no customization.
FieldLimitWhat it does
Name100 charactersHow you find it in the Voice list. Readers never see it.
Assistant name60 charactersWhat the assistant calls itself when asked. Empty means it does not give a name.
Response style400 charactersDefault, Friendly, Formal, Technical, or Describe it yourself… in your own words.
Language400 charactersWhich language to answer in, for example Answer in the language of the question.
Additional instructions4,000 charactersStyle rules: formatting, terminology, length.
Guardrail instructions4,000 charactersWhat to refuse and where to send readers when it cannot answer. Applied last.
A customization is a complete voice. Picking one replaces the knowledge base’s persona, tone and instructions; it does not merge with them. Deleting a customization never breaks anything. Each surface that used it goes back to its knowledge base’s persona.

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Good to know

  • Language: without a Language setting, answers are written in English unless the reader asks for another language. To answer in the reader’s language, say so in a customization’s Language field.
  • Several knowledge bases at once: when Ask searches several knowledge bases in one question, the persona comes from the first knowledge base selected.
  • Some rules cannot be changed. Citations, answer formatting, and declining when your sources do not cover a question always apply. Instructions cannot make the assistant answer when nothing relevant was found.
  • Test after changing a voice. Ask the same handful of real questions before and after. Instructions guide the model strongly, but not perfectly.

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From the API

Knowledge base persona fields are part of the knowledge base: 
curl -X PATCH https://app.kelu.dev/api/v1/knowledge-bases/$KB_ID \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "persona_prompt": "You are Aria, a support assistant for Acme Corp.",
    "tone": "friendly",
    "custom_instructions": "Recommend support@acme.com for billing questions."
  }'
Send "" to clear a field. Leave a field out to keep its current value.