unity-mcp-patterns

Unity MCP Patterns

The unity-mcp server gives Claude Code direct control over the Unity Editor. These patterns ensure you use it efficiently and safely.

Rule 1: batch_execute for Everything

Individual MCP calls have network overhead. batch_execute bundles multiple operations into one call — 10-100x faster.

// BAD — 5 separate calls, 5 round trips
manage_gameobject → create Player
manage_components → add Rigidbody2D to Player
manage_components → add BoxCollider2D to Player
manage_components → add SpriteRenderer to Player
manage_components → configure Rigidbody2D

// GOOD — 1 batch call
batch_execute → [
  create Player,
  add Rigidbody2D,
  add BoxCollider2D,
  add SpriteRenderer,
  configure Rigidbody2D
]

Always batch when doing 2+ operations.

Rule 2: read_console After Every Change

After writing scripts, creating objects, or modifying components, always check the console:

1. Write/Edit C# file
2. read_console → check for compilation errors
3. If errors: fix and repeat
4. Continue with MCP operations
5. read_console → check for runtime warnings

The console is your feedback loop. Don't assume operations succeeded.

Rule 3: project_info Before Assumptions

Before making decisions about the project, read its state:

project_info resource → Unity version, platform, render pipeline

Don't assume:

• The project uses URP (might be Built-in or HDRP)
• The project targets PC (might be mobile)
• Certain packages are installed

Rule 4: Tool Selection Guide

| Task | Tool | Key Actions | |------|------|-------------| | Create/load/save scene | manage_scene | create, load, save, validate | | Create/modify GameObjects | manage_gameobject | create, modify, delete, find | | Add/configure components | manage_components | add, remove, configure, get | | Physics setup | manage_physics | settings, layers, materials, joints | | Camera/Cinemachine | manage_camera | create, configure presets, extensions | | Materials/Shaders | manage_material / manage_shader | create, assign, configure | | Animation | manage_animation | clips, controllers, states | | UI elements | manage_ui | create, layout, style | | VFX | manage_vfx | particles, effects | | Prefabs | manage_prefabs | create, instantiate, modify | | ScriptableObjects | manage_scriptable_object | create, edit | | Packages | manage_packages | install, remove, search | | Builds | manage_build | configure, build, switch platform | | Tests | run_tests | execute, get results | | Profiling | manage_profiler | sessions, timing, memory | | Graphics stats | manage_graphics | rendering stats, pipeline | | Console output | read_console | errors, warnings, logs | | API inspection | unity_reflect | live C# reflection | | Documentation | unity_docs | official Unity docs | | C# scripts | create_script / validate_script | create, validate |

Rule 5: Scene Templates

When creating new scenes, use templates for quick setup:

manage_scene action:"create" template:"3d_basic"
// Creates scene with: Main Camera, Directional Light

manage_scene action:"create" template:"2d_basic"
// Creates scene with: Main Camera (orthographic)

Rule 6: Error Recovery

If an MCP operation fails:

1. read_console — get the error message
2. Fix the underlying issue (missing reference, wrong type, etc.)
3. Retry the operation
4. If the error persists, fall back to writing an Editor script

Rule 7: MCP vs File Editing

| Operation | Use MCP | Use File Edit | |-----------|---------|---------------| | Create GameObjects | Yes | Never | | Edit scenes | Yes | Never | | Edit prefabs | Yes | Never | | Write C# scripts | Either | Preferred for complex scripts | | Configure components | Yes | Never | | Modify ProjectSettings | Yes | Never | | Edit .shader/.hlsl files | No (Write tool) | Yes | | Edit .uxml/.uss files | No (Write tool) | Yes | | Edit .asmdef files | No (Write tool) | Yes |

Rule 8: Multi-Instance

If the user has multiple Unity Editor instances:

unity_instances resource → list all running editors
set_active_instance → route commands to specific editor

Always check which instance is active before sending commands.