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The persona parameter controls the base personality of every completion. An E.V.I. (Embedded Virtual Intelligence) is a pre-configured Theo client with a custom persona, skills, and tools baked in — your users interact with your brand, not Theo.

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Persona Options

ValueBehavior
"theo"Theo’s default personality — a sarcastic, brilliant robot from Jupiter. Witty, confident, and genuinely helpful underneath the snark.
"none"Neutral assistant with no personality
{ system_prompt: "..." }Your custom persona — replaces Theo entirely
// Custom persona
const res = await theo.complete({
  prompt: "Draft a follow-up email",
  persona: { system_prompt: "You are Eva, a professional CRM assistant for AcmeCorp." },
});

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E.V.I. — The SDK Shortcut

Instead of passing persona, skills, and tools on every request, create an E.V.I. instance: 
const evi = theo.evi({
  persona: "You are Nova, an operations assistant for WarehouseOS. Professional, concise, proactive.",
  skills: ["inventory-check", "data-extraction"],
  tools: [
    {
      name: "check_stock",
      description: "Look up current stock levels for a SKU",
      input_schema: {
        type: "object",
        properties: { sku: { type: "string" } },
        required: ["sku"],
      },
    },
  ],
  defaultMode: "auto",
});

// Every call through the E.V.I. includes the persona, skills, and tools automatically
const res = await evi.complete({ prompt: "Check stock levels for SKU-1234" });

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Three Levels

  1. Persona only — Replace Theo’s voice with your brand
  2. Persona + Skills — Add domain expertise (inventory, compliance, etc.)
  3. Persona + Skills + Inline Tools — Connect Theo to your product’s actions
See the full E.V.I. Guide for detailed examples of each level.

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E.V.I. Canvas — The Visual Builder

Prefer a visual approach? The E.V.I. Canvas is a drag-and-drop skill builder in the dashboard. Design node graphs with prompts, models, tools, knowledge, vision, and conditions — then compile, test, and publish without writing a manifest. See the Canvas Guide and Canvas SDK Reference.