> ## Documentation Index
> Fetch the complete documentation index at: https://docs.hitheo.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Build an E.V.I.

> Embed Theo into your product with a custom persona, skills, and tools.

An E.V.I. (Embedded Virtual Intelligence) is Theo embedded in your product. Your users interact with your branded AI, powered by Theo's orchestration engine.

## What You're Building

```
Your Application (CRM, dashboard, app)
  └── Your UI (chat, sidebar, actions)
        └── @hitheo/sdk (evi instance)
              └── Theo API (api.hitheo.ai)
                    └── Classify → Skills → Route → Agent Loop → Response
```

## Level 1: Custom Persona Only

```typescript theme={null}
const evi = theo.evi({
  persona: "You are Kai, a friendly coding assistant for DevHub.",
});

const res = await evi.complete({
  prompt: "Why is my useEffect running twice?",
});
```

## Level 2: Persona + Skills

```typescript theme={null}
const evi = theo.evi({
  persona: "You are Atlas, an operations assistant for AcmeCorp.",
  skills: ["inventory-check", "data-extraction"],
});
```

## Level 3: Persona + Skills + Inline Tools

```typescript theme={null}
const evi = theo.evi({
  persona: "You are Nova, the AI assistant for WarehouseOS.",
  skills: ["data-extraction"],
  tools: [
    {
      name: "check_inventory",
      description: "Look up stock levels for a SKU",
      input_schema: {
        type: "object",
        properties: { sku: { type: "string" } },
        required: ["sku"],
      },
    },
  ],
});
```

## Streaming

```typescript theme={null}
const stream = evi.stream({ prompt: "Generate inventory report" });
for await (const event of stream) {
  if (event.type === "token") process.stdout.write(event.token!);
}
```

## Best Practices

* **Persona**: Be specific about what the E.V.I. should NOT do ("Never mention Theo")
* **Skills**: Install only what your use case needs
* **Tools**: Keep descriptions clear — the model reads them to decide when to call
* **Cost**: Use `mode: "fast"` for simple queries