> ## 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.

# Activating Skills via API

> How to find skill slugs, pass them in API calls, and use them from the SDK.

Skills extend Theo with specialized capabilities — domain knowledge, custom tools, prompt extensions, and model preferences. You can activate skills on any completion request by passing their **slug**.

## Finding a Skill Slug

Every skill has a unique slug (e.g., `customer-support`, `code-review`, `deep-research`).

**In the Dashboard:**

1. Go to **Skills → Marketplace** or **My Skills**.
2. Each skill card displays its slug — click the copy icon to copy it.

**Via API:**

```bash theme={null}
# List all marketplace skills
curl -H "Authorization: Bearer $THEO_API_KEY" \
  https://www.hitheo.ai/api/v1/skills

# List your installed skills
curl -H "Authorization: Bearer $THEO_API_KEY" \
  "https://www.hitheo.ai/api/v1/skills?filter=installed"
```

Both return a `skills` array. Each object includes `slug`, `name`, `description`, and `category`.

**In the E.V.I. Canvas:**
When you open the Input node with **API Call** trigger, the canvas shows the skill's slug with a **Copy** button. If the canvas hasn't been published yet, it shows the draft slug preview.

## Using Skills in a Completion

Pass one or more slugs in the `skills` array:

<CodeGroup>
  ```bash curl theme={null}
  curl -X POST https://www.hitheo.ai/api/v1/completions \
    -H "Authorization: Bearer $THEO_API_KEY" \
    -H "Content-Type: application/json" \
    -d '{
      "prompt": "Summarize recent support tickets for this customer",
      "skills": ["customer-support"]
    }'
  ```

  ```typescript SDK theme={null}
  import { Theo } from "@hitheo/sdk";

  const theo = new Theo({ apiKey: process.env.THEO_API_KEY! });

  const res = await theo.complete({
    prompt: "Summarize recent support tickets for this customer",
    skills: ["customer-support"],
  });
  ```

  ```python Python (requests) theme={null}
  import requests

  res = requests.post(
      "https://www.hitheo.ai/api/v1/completions",
      headers={"Authorization": f"Bearer {THEO_API_KEY}"},
      json={
          "prompt": "Summarize recent support tickets for this customer",
          "skills": ["customer-support"],
      },
  )
  ```
</CodeGroup>

## How It Works

When you pass `skills`:

1. **Slug resolution** — Theo looks up each slug and loads the skill's manifest (prompt extension, tools, model preference).
2. **Merge with installed skills** — The requested skills are merged with any skills you already have installed and enabled.
3. **Prompt injection** — Each active skill's system prompt extension is injected into the request context, ordered by priority and intensity.
4. **Tool aggregation** — Tools declared by active skills become available to the agent loop.
5. **Model preference** — If a skill specifies a preferred model (e.g., `theo-1-reason` for deep analysis), Theo may route to that model.

## Multiple Skills

You can activate multiple skills simultaneously:

```json theme={null}
{
  "prompt": "Extract data from the attached ACORD 125 form and run a compliance check",
  "skills": ["data-extraction", "insurance-compliance"]
}
```

Skills are applied in the order listed. If skills have conflicting model preferences, the first skill's preference takes precedence.

## Skills You Don't Have Installed

You can pass the slug of **any public skill** in the `skills` array — you don't need to install it first. Installing a skill means it's automatically included in every request; passing it in `skills` activates it for a single request.

## Building Your Own Skill

See [Build with the E.V.I. Canvas](/guides/evi-canvas) to create skills visually, or use the SDK:

```typescript theme={null}
import { defineSkill } from "@hitheo/sdk";

export default defineSkill({
  name: "my-custom-skill",
  tools: [myTool],
  knowledge: ["./docs/*.md"],
});

// Publish: npx theo publish
```

After publishing, your skill's slug is available for use in `skills` arrays immediately.