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

# Flat SubAgents

> Add a SubAgent definition that does not need private instructions or capabilities.

Use a flat file for a small SubAgent that needs only its definition.

From a managed ADK agent's root, create the discovered starter:

```bash theme={null}
harnest add subagent researcher
```

The command refuses to overwrite an existing definition. Use `--project <agent-root>` when running it from elsewhere. LangGraph graphs define SubAgent topology explicitly in `agent.py`; see [framework behavior](/docs/harnest/build/subagents/framework-behavior).

```text theme={null}
subagents/
└── researcher.py
```

`subagents/researcher.py` exports an `Agent` named `researcher`.

## Flat SubAgent properties

| Property             | Rule                                 |
| -------------------- | ------------------------------------ |
| File                 | `subagents/<name>.py`                |
| Export               | Must match the filename              |
| Instructions         | Defined by the agent declaration     |
| Private tools        | Not supported                        |
| Private MCP          | Not supported                        |
| Private Agent Skills | Not supported                        |
| Use from parent      | Reference by name or as a graph node |

Move the SubAgent into a folder when it needs private instructions or capabilities.

<Card title="Folder-owned SubAgents" icon="folder" href="/docs/harnest/build/subagents/folder-subagents">
  Create a separate capability boundary for the child agent.
</Card>