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

# Quickstart

> Build and install your first Agent Harness in minutes.

# Quickstart

This guide walks you through creating a minimal harness from scratch.

## Prerequisites

* An AI client that supports Agent Harnesses (see [Clients](/clients))
* Basic familiarity with markdown

## Step 1 — Create the harness directory

```bash theme={null}
mkdir my-first-harness
cd my-first-harness
```

## Step 2 — Write HARNESS.md

`HARNESS.md` is the only required file. Create it now:

```markdown theme={null}
---
name: Writing Assistant
description: Helps draft, edit, and improve written content.
---

You are a writing assistant. Help the user draft, revise, and polish written content.
Adapt your tone to the context: formal for business documents, conversational for blog posts.
```

That's a valid harness. You can stop here and install it in your client.

## Step 3 — Add a skill (optional)

Create a skill to give your agent a specific, reusable capability:

```bash theme={null}
mkdir -p skills/summarize
```

```markdown theme={null}
# skills/summarize/SKILL.md
---
name: Summarize
description: Condense a piece of text into a concise summary.
---

To summarize a document:
1. Read the full text provided by the user.
2. Identify the main argument or purpose.
3. Extract the 3–5 most important supporting points.
4. Write a summary of 3–5 sentences using plain language.
5. Do not add information that isn't in the source text.
```

Create a `.leaf-detectors` file at the harness root so clients know to treat directories containing `SKILL.md` as skill leaves:

```
# .leaf-detectors
skill=SKILL.md
```

Without this file, a compliant client will traverse into `skills/summarize/` as an ordinary directory rather than activating it as a skill.

Update `HARNESS.md` to reference it:

```markdown theme={null}
---
name: Writing Assistant
description: Helps draft, edit, and improve written content.
---

You are a writing assistant. Help the user draft, revise, and polish written content.

- `skills/summarize` — condense any text into a concise summary
```

## Step 4 — Add a directory (optional)

You can add any top-level directory to bundle context relevant to your domain. The directory name is up to you. Create a routing file named after it in all-caps to help the agent navigate its contents:

```bash theme={null}
mkdir context
```

```markdown theme={null}
# context/CONTEXT.md
---
description: Style and tone guidelines that apply to all written output.
---

Consult this directory for rules that govern how the agent should write.

- `style-guide.md` — tone, formatting, and sentence-length rules
```

```markdown theme={null}
# context/style-guide.md
---
description: Tone and formatting rules that apply to all written output.
---

- Use active voice wherever possible.
- Prefer short sentences (under 25 words).
- Avoid jargon unless the user's context is clearly technical.
- Headings use sentence case, not title case.
```

Update `HARNESS.md`:

```markdown theme={null}
---
name: Writing Assistant
description: Helps draft, edit, and improve written content.
---

You are a writing assistant. Help the user draft, revise, and polish written content.

- `skills/summarize` — condense any text into a concise summary
- `context/` — style and tone guidelines (see CONTEXT.md)
```

## Step 5 — Install the harness

Refer to your AI client's documentation for how to install a local harness directory. Typically this involves pointing the client at the harness root folder.

## What's next

* [Best Practices](/harness-creation/best-practices) — learn how to structure harnesses for maintainability
* [Optimizing Descriptions](/harness-creation/optimizing-descriptions) — write descriptions that help agents activate the right skills
* [Evaluating Harnesses](/harness-creation/evaluating-harnesses) — test that your harness behaves as expected