assets-modify

Development

Modify an asset file in the project. Use 'assets-get-data' first to inspect the asset structure before modifying. Not allowed to modify asset files in the 'Packages/' folder — modify them in 'Assets/'. Three modification surfaces are available (content, pathPatches, jsonPatch) — see the skill body for details.

QUICK START

How to use this skill

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Open your project in Codex.
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Prompt to paste

I want to install this Agent Skill for this project in Codex.

Source SKILL.md: https://github.com/IvanMurzak/Unity-MCP/blob/HEAD/Unity-MCP-Plugin/.claude/skills/assets-modify/SKILL.md

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First, summarize what it does, its dependencies, license status if identifiable, and any risks. Show the exact files you propose to add under .agents/skills/assets-modify/. Do not write files or run scripts until I approve.

After I approve, install the complete skill folder, including required referenced files, into that project location. Verify it is discoverable, then tell me its actual invocation name and how to use it. Do not claim it is installed until you have verified it.

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Assets / Modify

Three modification surfaces

Use whichever fits the task:

content — full SerializedMember override (legacy, backwards compatible).
pathPatches — list of {path, value} pairs routed through Reflector.TryModifyAt.
jsonPatch — JSON Merge Patch routed through Reflector.TryPatch.

When more than one is supplied they run in this order: jsonPatch → pathPatches → content. At least one is required.

Path syntax

fieldName, nested/field, arrayField/[i], dictField/[key]. Leading #/ is stripped.

How to Call

unity-mcp-cli run-tool assets-modify --input '{
  "assetRef": "string_value",
  "content": "string_value",
  "pathPatches": "string_value",
  "jsonPatch": "string_value"
}'

For complex input (multi-line strings, code), save the JSON to a file and use:
unity-mcp-cli run-tool assets-modify --input-file args.json
Or pipe via stdin (recommended):
unity-mcp-cli run-tool assets-modify --input-file - <<'EOF'
{"param": "value"}
EOF

Troubleshooting

If unity-mcp-cli is not found, either install it globally (npm install -g unity-mcp-cli) or use npx unity-mcp-cli instead. Read the /unity-initial-setup skill for detailed installation instructions.

Input

Name	Type	Required	Description
`assetRef`	`any`	Yes	Reference to UnityEngine.Object asset instance. It could be Material, ScriptableObject, Prefab, and any other Asset. Anything located in the Assets and Packages folders.
`content`	`any`	No	Optional. The asset content. It overrides the existing asset content (legacy path).
`pathPatches`	`any`	No	Optional. List of path-scoped patches routed through Reflector.TryModifyAt.
`jsonPatch`	`any`	No	Optional. JSON Merge Patch (RFC 7396, extended with [i]/[key] keys) routed through Reflector.TryPatch.

Input JSON Schema

{
  "type": "object",
  "properties": {
    "assetRef": {
      "$ref": "#/$defs/AIGD.AssetObjectRef"
    },
    "content": {
      "$ref": "#/$defs/com.IvanMurzak.ReflectorNet.Model.SerializedMember"
    },
    "pathPatches": {
      "$ref": "#/$defs/System.Collections.Generic.List(AIGD.PathPatch)"
    },
    "jsonPatch": {
      "anyOf": [
        {
          "type": "string"
        },
        {
          "type": "object",
          "additionalProperties": true
        }
      ]
    }
  },
  "$defs": {
    "System.Type": {
      "type": "string"
    },
    "AIGD.AssetObjectRef": {
      "type": "object",
      "properties": {
        "instanceID": {
          "type": "integer",
          "description": "instanceID of the UnityEngine.Object. If this is '0' and 'assetPath' and 'assetGuid' is not provided, empty or null, then it will be used as 'null'."
        },
        "assetType": {
          "$ref": "#/$defs/System.Type",
          "description": "Type of the asset."
        },
        "assetPath": {
          "type": "string",
          "description": "Path to the asset within the project. Starts with 'Assets/'"
        },
        "assetGuid": {
          "type": "string",
          "description": "Unique identifier for the asset."
        }
      },
      "required": [
        "instanceID"
      ],
      "description": "Reference to UnityEngine.Object asset instance. It could be Material, ScriptableObject, Prefab, and any other Asset. Anything located in the Assets and Packages folders."
    },
    "com.IvanMurzak.ReflectorNet.Model.SerializedMemberList": {
      "type": "array",
      "items": {
        "$ref": "#/$defs/com.IvanMurzak.ReflectorNet.Model.SerializedMember"
      }
    },
    "com.IvanMurzak.ReflectorNet.Model.SerializedMember": {
      "type": "object",
      "properties": {
        "typeName": {
          "type": "string",
          "description": "Full type name. Eg: 'System.String', 'System.Int32', 'UnityEngine.Vector3', etc."
        },
        "name": {
          "type": "string",
          "description": "Object name."
        },
        "value": {
          "description": "Value of the object, serialized as a non stringified JSON element. Can be null if the value is not set. Can be default value if the value is an empty object or array json."
        },
        "fields": {
          "type": "array",
          "items": {
            "$ref": "#/$defs/com.IvanMurzak.ReflectorNet.Model.SerializedMember",
            "description": "Nested field value."
          },
          "description": "Fields of the object, serialized as a list of 'SerializedMember'."
        },
        "props": {
          "type": "array",
          "items": {
            "$ref": "#/$defs/com.IvanMurzak.ReflectorNet.Model.SerializedMember",
            "description": "Nested property value."
          },
          "description": "Properties of the object, serialized as a list of 'SerializedMember'."
        }
      },
      "required": [
        "typeName"
      ],
      "additionalProperties": false
    },
    "AIGD.PathPatch": {
      "type": "object",
      "properties": {
        "Path": {
          "type": "string",
          "description": "Slash-delimited path to the target field/element/entry. Plain segment navigates a field or property (e.g. 'admin' or 'admin/name'). Use '[i]' for array/list index (e.g. 'planets/[0]/orbitRadius'). Use '[key]' for dictionary entry (e.g. 'config/[timeout]'). A leading '#/' is stripped automatically. Required."
        },
        "Value": {
          "$ref": "#/$defs/com.IvanMurzak.ReflectorNet.Model.SerializedMember",
          "description": "The new value to write at the path. Use the standard SerializedMember envelope: 'typeName' + 'value' for primitives, or nested 'fields'/'props' for complex types. Required — omitting it overwrites the target with a default empty SerializedMember."
        }
      }
    },
    "System.Collections.Generic.List(AIGD.PathPatch)": {
      "type": "array",
      "items": {
        "$ref": "#/$defs/AIGD.PathPatch"
      }
    }
  },
  "required": [
    "assetRef"
  ]
}

Output

Output JSON Schema

{
  "type": "object",
  "properties": {
    "result": {
      "$ref": "#/$defs/System.String-1"
    }
  },
  "$defs": {
    "System.String-1": {
      "type": "array",
      "items": {
        "type": "string"
      }
    }
  },
  "required": [
    "result"
  ]
}