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

# Agent concepts

> Understand the concepts Harnest composes and where each concept is authored.

A Harnest agent is an inspectable directory. Each concept has one conventional location:

| Concept                                                                             | Project source                  | Purpose                                                  |
| ----------------------------------------------------------------------------------- | ------------------------------- | -------------------------------------------------------- |
| [Project Configuration](/harnest/build/project-configuration)                       | Root YAML, TOML, and lock files | Runtime, discovery, server, and dependency configuration |
| [Agents and Graphs](/harnest/build/agents-and-graphs)                               | `agent.py`, `instructions.md`   | Root agent or graph and its instructions                 |
| [Data Models and Shared Libraries](/harnest/build/data-models-and-shared-libraries) | `models/`, `lib/`               | Shared contracts and ordinary reusable Python            |
| [Agent Tools](/harnest/build/agent-tools)                                           | `tools/`                        | Server tools and client-hosted tool declarations         |
| [SubAgents](/harnest/build/subagents)                                               | `subagents/`                    | Flat definitions and separately owned agent bundles      |
| [MCP Client](/harnest/build/mcp-client)                                             | `mcp/`                          | Direct MCP server connections                            |
| [Agent Plugins](/harnest/build/agent-plugins)                                       | `plugins/`                      | Reusable MCP-and-skill capability bundles                |
| [Agent Skills](/harnest/build/agent-skills)                                         | `skills/`                       | Progressively loaded task guidance                       |
| [Lifecycle](/harnest/runtime/lifecycle)                                             | `extensions/`                   | Hooks, resources, storage, and native integrations       |
| [Sandboxing](/harnest/build/sandboxing)                                             | `sandbox/`                      | Optional ADK code-execution backend                      |
| [Testing and Compilation](/harnest/build/testing-and-compilation)                   | `evals/`, `tests/`              | Evals, unit tests, live smoke tests, and artifacts       |

[Authentication and Credentials](/harnest/runtime/authentication-and-credentials) and [Telemetry](/harnest/runtime/telemetry) have separate security and privacy contracts.

## Discovery rules

| Rule                            | What it means                              |
| ------------------------------- | ------------------------------------------ |
| Optional folders may be absent  | Add only the capabilities you need         |
| Public filenames are identities | Match each required export to its filename |
| Location drives discovery       | Do not register sibling resources manually |
| `.harnest/` is generated        | Do not edit or commit it                   |
| `uv.lock` is project source     | Commit it for repeatable environments      |

`harnest init` creates the required root files. Use `--example` for active examples; the default scaffold keeps optional folders as guides.

## Coding-agent guide

Install Harnest's bundled project-editing guidance for a coding agent:

```bash theme={null}
harnest skills install
```

Use `--target` or `--project` when auto-detection is wrong. This coding guide is separate from runtime Agent Skills.