Quickstart

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

Prerequisites

An AI client that supports Agent Harnesses (see Clients)
Basic familiarity with markdown

Step 1 — Create the harness directory

mkdir my-first-harness
cd my-first-harness

Step 2 — Write HARNESS.md

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

---
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:

mkdir -p skills/summarize

# 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:

---
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:

mkdir context

# 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

# 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:

---
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 — learn how to structure harnesses for maintainability
Optimizing Descriptions — write descriptions that help agents activate the right skills
Evaluating Harnesses — test that your harness behaves as expected

For harness creators

For client implementors

Quickstart

Quickstart

Prerequisites

Step 1 — Create the harness directory

Step 2 — Write HARNESS.md

Step 3 — Add a skill (optional)

Step 4 — Add a directory (optional)

Step 5 — Install the harness

What’s next

​Quickstart

​Prerequisites

​Step 1 — Create the harness directory

​Step 2 — Write HARNESS.md

​Step 3 — Add a skill (optional)

​Step 4 — Add a directory (optional)

​Step 5 — Install the harness

​What’s next

Quickstart

Prerequisites

Step 1 — Create the harness directory

Step 2 — Write HARNESS.md

Step 3 — Add a skill (optional)

Step 4 — Add a directory (optional)

Step 5 — Install the harness

What’s next