Unity-MCP Operator Guide

This skill helps you effectively use the Unity Editor with MCP tools and resources.

Template Notice

Examples in references/workflows.md and references/tools-reference.md are reusable templates. They may be inaccurate across Unity versions, package setups (UGUI/TMP/Input System), and project-specific conventions. Please check console, compilation errors, or use screenshot after implementation.

Before applying a template:

• Validate targets/components first via resources and find_gameobjects.
• Treat names, enum values, and property payloads as placeholders to adapt.

Resource URIs: Do NOT Guess

Resource URIs use a specific scheme — do NOT guess or fabricate them. If you are unsure of a URI, call ListMcpResourcesTool(server="UnityMCP") first to get the exact list. Common URIs:

Resource	URI
Editor state	mcpforunity://editor/state
Project info	mcpforunity://project/info
Scene GameObject API	mcpforunity://scene/gameobject-api
Tags	mcpforunity://project/tags
Layers	mcpforunity://project/layers
Instances	mcpforunity://instances
Custom tools	mcpforunity://custom-tools

Quick Start: Resource-First Workflow

Always read relevant resources before using tools. This prevents errors and provides the necessary context.

1. Check editor state     → mcpforunity://editor/state
2. Understand the scene   → mcpforunity://scene/gameobject-api
3. Find what you need     → find_gameobjects or resources
4. Take action            → tools (manage_gameobject, create_script, script_apply_edits, apply_text_edits, validate_script, delete_script, get_sha, etc.)
5. Verify results         → read_console, capture_screenshot (in manage_scene), resources

Critical Best Practices

1. After Writing/Editing Scripts: Always Refresh and Check Console

# After create_script or script_apply_edits:
refresh_unity(mode="force", scope="scripts", compile="request", wait_for_ready=True)
read_console(types=["error"], count=10, include_stacktrace=True)

Why: Unity must compile scripts before they're usable. Compilation errors block all tool execution.

2. Use batch_execute for Multiple Operations

# 10-100x faster than sequential calls
batch_execute(
    commands=[
        {"tool": "manage_gameobject", "params": {"action": "create", "name": "Cube1", "primitive_type": "Cube"}},
        {"tool": "manage_gameobject", "params": {"action": "create", "name": "Cube2", "primitive_type": "Cube"}},
        {"tool": "manage_gameobject", "params": {"action": "create", "name": "Cube3", "primitive_type": "Cube"}}
    ],
    parallel=True  # Hint only: Unity may still execute sequentially
)

Max 25 commands per batch by default (configurable in Unity MCP Tools window, max 100). Use fail_fast=True for dependent operations.

3. Use Screenshots to Verify Visual Results

Screenshot Parameters

Parameter	Type	Description
camera	string	Camera name/path/ID. Defaults to Camera.main
include_image	bool	Return base64 PNG inline (for AI vision)
max_resolution	int	Max longest-edge pixels (default 640). Lower = smaller payload
supersize	int	Resolution multiplier 1–4 for file-saved screenshots
batch	string	"surround" (6 fixed angles) or "orbit" (configurable grid)
look_at	string	Target: GameObject name/path/ID, or "x,y,z" world position
view_position	list	Camera position [x,y,z] for positioned screenshot
view_rotation	list	Camera euler rotation [x,y,z] for positioned screenshot
orbit_angles	int	Number of azimuth samples around the target (default 8)
orbit_elevations	list	Vertical angles in degrees, e.g. [0, 30, -15] (default [0, 30, -15])
orbit_distance	float	Camera distance from target in world units (auto-calculated if omitted)
orbit_fov	float	Camera field of view in degrees (default 60)

Single Screenshots

# Basic screenshot (saves to Assets/Screenshots/, returns file path)
manage_scene(action="screenshot")

# Inline screenshot (returns base64 PNG directly to the AI)
manage_scene(action="screenshot", include_image=True)

# Specific camera + capped resolution for smaller payloads
manage_scene(action="screenshot", camera="MainCamera", include_image=True, max_resolution=512)

# Positioned screenshot: place a temp camera at a specific viewpoint
manage_scene(action="screenshot", look_at="Player", view_position=[0, 10, -10], max_resolution=512)

Batch Screenshots (Contact Sheet)

Batch modes return a single composite contact sheet image — a grid of labeled thumbnails — instead of separate files. This is ideal for AI scene understanding in one image.

# Surround: 6 fixed angles (front/back/left/right/top/bird_eye)
manage_scene(action="screenshot", batch="surround", max_resolution=256)

# Surround centered on a specific object
manage_scene(action="screenshot", batch="surround", look_at="Player", max_resolution=256)

# Orbit: 8 angles at eye level around an object
manage_scene(action="screenshot", batch="orbit", look_at="Player", orbit_angles=8)

# Orbit: 10 angles, 3 elevation rings, custom distance
manage_scene(action="screenshot", batch="orbit", look_at="Player",
             orbit_angles=10, orbit_elevations=[0, 30, -15], orbit_distance=8)

# Orbit: tight close-up with narrow FOV
manage_scene(action="screenshot", batch="orbit", look_at="Treasure",
             orbit_distance=3, orbit_fov=40, orbit_angles=6)

Best practices for AI scene understanding:

• Use include_image=True when you need to see the scene, not just save a file.
• Use batch="surround" for a quick 6-angle overview of the whole scene.
• Use batch="orbit" for detailed inspection of a specific object from many angles.
• Keep max_resolution at 256–512 to balance quality vs. token cost.
• Use orbit_elevations to get views from above/below, not just around.
• Omit orbit_distance to let Unity auto-fit the object in frame.

# Agentic camera loop: point, shoot, analyze
manage_gameobject(action="look_at", target="MainCamera", look_at_target="Player")
manage_scene(action="screenshot", camera="MainCamera", include_image=True, max_resolution=512)
# → Analyze image, decide next action

4. Check Console After Major Changes

read_console(
    action="get",
    types=["error", "warning"],  # Focus on problems
    count=10,
    format="detailed"
)

5. Always Check editor_state Before Complex Operations

# Read mcpforunity://editor/state to check:
# - is_compiling: Wait if true
# - is_domain_reload_pending: Wait if true  
# - ready_for_tools: Only proceed if true
# - blocking_reasons: Why tools might fail

Parameter Type Conventions

These are common patterns, not strict guarantees. manage_components.set_property payload shapes can vary by component/property; if a template fails, inspect the component resource payload and adjust.

Vectors (position, rotation, scale, color)

# Both forms accepted:
position=[1.0, 2.0, 3.0]        # List
position="[1.0, 2.0, 3.0]"     # JSON string

Booleans

# Both forms accepted:
include_inactive=True           # Boolean
include_inactive="true"         # String

Colors

# Auto-detected format:
color=[255, 0, 0, 255]         # 0-255 range
color=[1.0, 0.0, 0.0, 1.0]    # 0.0-1.0 normalized (auto-converted)

Paths

# Assets-relative (default):
path="Assets/Scripts/MyScript.cs"

# URI forms:
uri="mcpforunity://path/Assets/Scripts/MyScript.cs"
uri="file:///full/path/to/file.cs"

Core Tool Categories

Category	Key Tools	Use For
Scene	manage_scene, find_gameobjects	Scene operations, finding objects
Objects	manage_gameobject, manage_components	Creating/modifying GameObjects
Scripts	create_script, script_apply_edits, refresh_unity	C# code management
Assets	manage_asset, manage_prefabs	Asset operations
Editor	manage_editor, execute_menu_item, read_console	Editor control
Testing	run_tests, get_test_job	Unity Test Framework
Batch	batch_execute	Parallel/bulk operations
UI	manage_ui, batch_execute with manage_gameobject + manage_components	UI Toolkit: Use manage_ui to create UXML/USS files, attach UIDocument, inspect visual trees. uGUI (Canvas): Use batch_execute for Canvas, Panel, Button, Text, Slider, Toggle, Input Field. Read mcpforunity://project/info first to detect uGUI/TMP/Input System/UI Toolkit availability. (see UI workflows)

Common Workflows

Creating a New Script and Using It

# 1. Create the script
create_script(
    path="Assets/Scripts/PlayerController.cs",
    contents="using UnityEngine;\n\npublic class PlayerController : MonoBehaviour\n{\n    void Update() { }\n}"
)

# 2. CRITICAL: Refresh and wait for compilation
refresh_unity(mode="force", scope="scripts", compile="request", wait_for_ready=True)

# 3. Check for compilation errors
read_console(types=["error"], count=10)

# 4. Only then attach to GameObject
manage_gameobject(action="modify", target="Player", components_to_add=["PlayerController"])

Finding and Modifying GameObjects

# 1. Find by name/tag/component (returns IDs only)
result = find_gameobjects(search_term="Enemy", search_method="by_tag", page_size=50)

# 2. Get full data via resource
# mcpforunity://scene/gameobject/{instance_id}

# 3. Modify using the ID
manage_gameobject(action="modify", target=instance_id, position=[10, 0, 0])

Running and Monitoring Tests

# 1. Start test run (async)
result = run_tests(mode="EditMode", test_names=["MyTests.TestSomething"])
job_id = result["job_id"]

# 2. Poll for completion
result = get_test_job(job_id=job_id, wait_timeout=60, include_failed_tests=True)

Pagination Pattern

Large queries return paginated results. Always follow next_cursor:

cursor = 0
all_items = []
while True:
    result = manage_scene(action="get_hierarchy", page_size=50, cursor=cursor)
    all_items.extend(result["data"]["items"])
    if not result["data"].get("next_cursor"):
        break
    cursor = result["data"]["next_cursor"]

Multi-Instance Workflow

When multiple Unity Editors are running:

# 1. List instances via resource: mcpforunity://instances
# 2. Set active instance
set_active_instance(instance="MyProject@abc123")
# 3. All subsequent calls route to that instance

Error Recovery

Symptom	Cause	Solution
Tools return "busy"	Compilation in progress	Wait, check editor_state
"stale_file" error	File changed since SHA	Re-fetch SHA with get_sha, retry
Connection lost	Domain reload	Wait ~5s, reconnect
Commands fail silently	Wrong instance	Check set_active_instance

Reference Files

For detailed schemas and examples:

• tools-reference.md: Complete tool documentation with all parameters
• resources-reference.md: All available resources and their data
• workflows.md: Extended workflow examples and patterns