Interface IUnityMcpTool

Interface for implementing class-based MCP tools with flexible parameter handling. Use this when your tool needs state management, complex initialization, or custom schema generation. For simpler tools with strongly-typed parameters, consider using IUnityMcpTool<TParams> instead.

Namespace: Unity.AI.MCP.Editor.ToolRegistry

Assembly: Unity.AI.MCP.Editor.dll

Syntax

public interface IUnityMcpTool

Remarks

Class-based tools are instantiated once at discovery time and reused for all executions. The class must have a parameterless constructor and be decorated with the McpToolAttribute.

Schema generation:

• If GetInputSchema() returns null, a default flexible schema is provided
• If GetOutputSchema() returns null, the system attempts to auto-generate from the return type

Thread safety: Execute may be called from Unity's main thread. Avoid blocking operations.

Examples

[McpTool("custom_tool", "Performs custom operations")]
public class CustomTool : IUnityMcpTool
{
    public Task<object> ExecuteAsync(object parameters)
    {
        var jobject = parameters as JObject;
        var action = jobject?["action"]?.Value<string>();

        return Task.FromResult<object>(new { success = true, result = $"Executed {action}" });
    }

    public object GetInputSchema()
    {
        return new
        {
            type = "object",
            properties = new
            {
                action = new { type = "string", description = "Action to perform" }
            },
            required = new[] { "action" }
        };
    }
}

Methods

ExecuteAsync(object)

Executes the tool asynchronously with the provided parameters from the MCP client.

Declaration

Task<object> ExecuteAsync(object parameters)

Parameters

Type	Name	Description
object	parameters	Parameters as JObject from MCP client, or null if no parameters provided

Returns

Type	Description
Task<object>	A task containing the tool execution result, which will be serialized to JSON. Can be an anonymous object, class instance, or primitive type

Remarks

Called on Unity's main thread when an MCP client invokes this tool. Parameters are provided as a Newtonsoft.Json.Linq.JObject for flexible access. Return values are automatically serialized to JSON for the MCP response. For synchronous tools, return Task.FromResult(result).

Exceptions

Type	Condition
Exception	Thrown exceptions are caught and returned as error responses to the MCP client

GetInputSchema()

Provides a custom JSON schema for this tool's input parameters.

Declaration

object GetInputSchema()

Returns

Type	Description
object	JSON schema object (typically an anonymous object with type/properties/required fields), or null to use default schema

Remarks

Optional: Return null to use a default flexible schema that accepts any object properties. The schema should follow JSON Schema specification and describe the expected parameter structure.

GetOutputSchema()

Provides a custom JSON schema for this tool's output structure.

Declaration

object GetOutputSchema()

Returns

Type	Description
object	JSON schema object describing the return value structure, or null for no output schema

Remarks

Optional: Return null for no output schema. The system will attempt to auto-generate a schema by inspecting the Execute method's return type, but this may not work for all types. Providing an explicit schema improves documentation and client-side typing.