skill-authoring git:20260917.afac548A

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---
name: skill-authoring
description: "Use this skill when creating, editing, or reviewing an Unreal Engine Agent Skill, a named bundle of instructions registered with the unreal-mcp server (distinct from Claude Code's harness skills under `.claude/skills/`). Trigger when the user wants to add or change a skill that the in-editor agent will load. Concrete triggers: 'create a new Agent Skill', 'add a skill for X workflow', 'edit/update this skill', 'review my skill', 'make a Python skill class', 'create a skill UAsset', 'register a skill so Claude/an agent picks it up'; writing or editing a `SKILL.md` inside a UE plugin's `Skills/` or `Python/skills/` folder; defining a Python skill class registered with the skill registry; calling `CreateSkill`, `ListSkills`, or `GetSkills` MCP tools; designing a skill's name, description, or instruction body. SKIP for: authoring a toolset (use create-toolset), invoking an existing skill at runtime (use unreal-mcp), editing harness-level Claude Code skills under `.claude/skills/` or `~/.claude/skills/`, or generic uses of the word 'skill'."
---

# Agent Skill Authoring

You are authoring an Unreal Engine Agent Skill: a named, reusable bundle of instructions that packages essential knowledge the agent either doesn't know or needs to pay close attention to. A skill can provide general best practices in a domain, guidance on a specific workflow, or a mix of both.

## Principles

A good skill is:

**Novel**: The content should be things the agent doesn't already know or can't learn by using tools. If the agent could figure it out by calling a tool, don't put it in a skill.

**Collegial**: Write like you're briefing a knowledgeable colleague, not authoring documentation. Assume the reader understands Unreal. Give them what they need to act, not a full explanation of how everything works.

**Flexible**: Skills can include conceptual explanations, step-by-step instructions, or a mix. Use whichever form makes the guidance clearest for the task.

**Durable**: Don't embed property names, tool names, or other details that change over time. Skills that reference specific API names break silently when those names change.

**Agnostic**: Don't reference orchestration systems, role names, model names, or anything about how the agent is wired up. Skills should work regardless of the surrounding infrastructure.

**Parsimonious**: Every token costs context. Put them where they matter most and cut anything that isn't essential or evergreen. If a sentence wouldn't be missed, remove it.

## Before You Write

Work through these questions before writing anything.

**1. Does the skill already exist?** Call `ListSkills` via MCP to see all registered skills in the project, then `GetSkills` on anything relevant. If the capability is already covered, point the user to the existing skill rather than creating a new one.

**2. Choose the implementation path.** Two paths exist and the choice depends on where the skill lives:

- **Python class**: The right choice when the skill is part of a code plugin. It lives alongside the plugin's Python toolsets, is version-controlled with the plugin, and is registered automatically when the plugin loads.
- **UAsset**: The right choice when the skill is project-specific and doesn't belong in a plugin. Create it directly in the Content Browser using `CreateSkill` via MCP. No code required.

## Structure

Every Unreal skill has two fields.

**Description**: Loaded at discovery time, before the skill's full instructions are read. One or two sentences that clearly describe what the skill covers and when it applies.

**Instructions**: The skill's payload. The actual guidance the agent follows when the skill is active. Apply the principles above: focus on what tools can't teach and cut anything not essential.

The agent discovers and dispatches tools at runtime through the unreal-mcp meta-tools (`list_toolsets`, `describe_toolset`, `call_tool`), so write instructions that assume the agent will find the tools it needs rather than naming a fixed toolset list.

## Python Skills

A Python skill is a `UAgentSkill` subclass defined in a Python file inside a plugin. Use this path when the skill belongs to a code plugin and should be version-controlled with the plugin.

### Authoring

Decorate the class with `@agent_skill` and inherit from `unreal.AgentSkill`. The two fields from the Structure section map to class attributes:

- The class docstring becomes the `Description`. Keep it to one or two sentences.
- `instructions` is a class attribute string containing the guidance loaded when the skill activates.

```python
import unreal

from toolset_registry.agent_skill import agent_skill

_INSTRUCTIONS = (
    'Do X before Y, because Z.\n'
    'Always verify the result after performing the operation.\n'
)

@agent_skill
class MySkill(unreal.AgentSkill):
    """Provides guidance on doing X in Unreal Engine.
    Apply this skill whenever the user wants to accomplish X."""

    instructions = _INSTRUCTIONS
```

### Registration

Skills register themselves on import. Unless directed otherwise, place skill files in a `skills/` subfolder within the plugin's Python package, import each one explicitly in that subfolder's `__init__.py`, and ensure `init_unreal.py` imports the `skills` package.

### Reloading

After editing a Python skill, reload the plugin's package before verifying. The editor won't pick up changes otherwise. Enable Remote Execution in **Edit → Project Settings → Plugins → Python → Enable Remote Execution**, then run:

```bash
python Engine/Plugins/Experimental/ToolsetRegistry/Content/Python/toolset_registry/tests/reload_remote.py your_plugin
```

## UAsset Skills

A UAsset skill is a `UAgentSkill` instance saved as a Content Browser asset. Use this path for project-specific skills that don't belong in a plugin and require no code.

### Authoring

Use `AgentSkillToolset` via MCP. Start by calling `ListSkills` to see what exists, then either create or update:

**Creating**: Call `CreateSkill` with:
- `FolderPath`: Content Browser folder, e.g. `/Game/Skills/`
- `AssetName`: PascalCase name, e.g. `MyWorkflowSkill`
- `Description`: one or two sentences (see Structure above)
- `Details`: a `FAgentSkillDetails` with `Instructions`

**Updating**: Call `UpdateSkill` with:
- `SkillPath`: full path to the skill, e.g. `/Game/Skills/MyWorkflowSkill.MyWorkflowSkill_C`
- `Description`: revised description
- `Details`: revised `FAgentSkillDetails`

## Reviewing Your Work

Before handing off, verify the skill looks right by calling `GetSkills` on its path. Then read the description and instructions together as the agent will see them:

- **Description**: Does it clearly say when this skill applies? Would an agent reading only the description know whether to activate it for a given task?
- **Instructions**: Do they teach something the agent couldn't learn from the tools? Are they brief enough to be worth the context cost?