Class McpDescriptionAttribute

Provides descriptions and constraints for MCP tool parameter properties. Applied to properties in parameter classes to enhance automatically generated schemas.

Inheritance
object
Attribute
McpDescriptionAttribute
Implements
Inherited Members
Namespace: Unity.AI.MCP.Editor.ToolRegistry
Assembly: Unity.AI.MCP.Editor.dll
Syntax
[AttributeUsage(AttributeTargets.Property|AttributeTargets.Field)]
public class McpDescriptionAttribute : Attribute, _Attribute
Remarks

This attribute enhances schema generation by providing:

  • Human-readable descriptions for properties
  • Required field markers
  • Enum constraints for string properties
  • Explicit default values (overriding property initializers)

The SchemaGenerator reads this attribute when generating input schemas for tools using typed parameters.

Examples
public class CreateObjectParams
{
    [McpDescription("Name of the object to create", Required = true)]
    public string Name { get; set; }

    [McpDescription("Object type", EnumType = typeof(ObjectType))]
    public string Type { get; set; } = "cube";

    [McpDescription("Scale multiplier", Default = 1.0)]
    public float Scale { get; set; }

    [McpDescription("Position in world space")]
    public Vector3 Position { get; set; }
}

public enum ObjectType { Cube, Sphere, Cylinder }

Constructors

McpDescriptionAttribute(string)

Creates a description attribute for an MCP tool parameter property.

Declaration
public McpDescriptionAttribute(string description)
Parameters
Type Name Description
string description

Human-readable description text that explains the parameter's purpose and expected values

Properties

Default

Gets or sets an explicit default value for this parameter. Takes precedence over property initializers when generating the JSON schema.

Declaration
public object Default { get; set; }
Property Value
Type Description
object
Remarks

When set, this value will be used in the JSON schema's "default" field. If not set, the schema generator will attempt to detect defaults from property initializers. For enum properties, the default will be automatically converted to its string representation.

Description

Gets the human-readable description for this parameter property. This appears in the generated JSON schema and helps MCP clients understand the parameter's purpose.

Declaration
public string Description { get; }
Property Value
Type Description
string

EnumType

Gets or sets an enum type to use for constraining string property values. The enum values will be converted to string constraints in the JSON schema.

Declaration
public Type EnumType { get; set; }
Property Value
Type Description
Type
Remarks

This is useful when you want to constrain a string property to specific values without changing the property type from string. If the property itself is an enum type, this is not needed.

HasDefault

Gets whether an explicit default value was set via the Default property. Used internally by SchemaGenerator to distinguish between null defaults and no defaults.

Declaration
public bool HasDefault { get; }
Property Value
Type Description
bool

Required

Gets or sets whether this parameter is required. Required parameters must be provided by the MCP client; optional parameters may be omitted.

Declaration
public bool Required { get; set; }
Property Value
Type Description
bool
Remarks

Value types without default values are automatically considered required. Set this to true to explicitly mark reference types as required.

Implements