add_type

[refactoring]

Creates a top-level C# type in a new file and returns a diff.

Before you use this tool

Writes files by default. Set applyChanges: false to preview the diff. Inspect the diff before application.

Parameters

Name	Type	Required	Description
typeCode	string	Yes	The full C# source of the type. May include using directives and one namespace.
filePath	string	Yes	The file to create. Absolute or loaded-root-relative. Must not already exist.
targetNamespace	string	No	The namespace for the type. If omitted, taken from the source or inferred from a sibling file.
projectName	string	No	Optional project name when the target directory is under more than one project.
applyChanges	boolean	No	If true (default), applies changes to disk. If false, returns a preview diff. Default: `true`
failOnErrors	boolean	No	If true, do not write when the edit introduces a compile error; the response reports the diagnostics. Default: `false`
includeDiff	boolean	No	Include unified diff in response. Default is true. Default: `true`
maxDiffChars	number	No	Max diff characters. Use 0 for unlimited. Default is 50000. Default: `50000`
includePerFileDiff	boolean	No	Include per-file diffs in changedFiles. Default is true. Default: `true`
pathStyle	string	No	Path style: 'absolute' (default) or 'relative' (to solution root). Default: `"absolute"`
responseDetail	string	No	compact returns results and actionable state. full adds diagnostic metadata under responseDiagnostics. Default: `"compact"`

Examples

Replace sample paths and symbol keys with values from your workspace.

Preview creating a new class

Arguments 
{
  "typeCode": "public class OrderService { }",
  "filePath": "src/Orders/OrderService.cs",
  "targetNamespace": "MyProject.Orders",
  "applyChanges": false
}

Full MCP request

Full MCP request 
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "add_type",
    "arguments": {
      "typeCode": "public class OrderService { }",
      "filePath": "src/Orders/OrderService.cs",
      "targetNamespace": "MyProject.Orders",
      "applyChanges": false
    }
  }
}

Illustrative response 
{
  "success": true,
  "typeName": "OrderService",
  "typeKind": "class",
  "namespace": "MyProject.Orders",
  "namespaceSource": "explicit",
  "filePath": "/path/to/OrderService.cs",
  "filesChanged": 1,
  "filesCreated": 1,
  "applied": false,
  "message": null,
  "diagnostics": {
    "errorCount": 0,
    "warningCount": 0,
    "items": []
  },
  "unifiedDiff": "...",
  "changedFiles": [
    {
      "filePath": "/path/to/OrderService.cs",
      "changeCount": 3,
      "diff": "..."
    }
  ],
  "workspaceUpdate": null
}

Response Notes

The source may include using directives and a single namespace. Chooses the project that owns the target path, infers the namespace from a sibling file when it is not given, and formats the created file. The target file must not already exist. For a partial type, an existing type of the same name is rejected.

Returns a unified diff of the created file (and any project-file edit). typeName, typeKind, namespace, and namespaceSource identify what was created and how the namespace was chosen. workspaceUpdate reports whether the workspace compiles the new file, and is null when nothing was created. diagnostics reports the compile errors and warnings the new file introduces; when failOnErrors is true and it introduces an error, applied is false and message explains why. In a multi-targeted project the check spans every target. Results use top-level fields with success. Compact is the default; full adds responseDiagnostics. Both modes retain errors, coverage, partial state, and recovery advice.