Xcode Diagnostics MCP Plugin

An MCP (Model Control Protocol) plugin for extracting and viewing errors and warnings from Xcode build logs.

Overview

This plugin implements the Model Control Protocol (MCP) specification to provide Xcode diagnostics functionality to any compatible AI assistants. It connects to Xcode's build system to extract, parse, and display diagnostics (errors and warnings) from your Swift projects. It helps AI assistants quickly identify issues in your code without having to manually search through build logs.

Note that since this works at the log level, Xcode must have already attempted a build before you run this tool.

Prerequisites

macOS operating system
Xcode installed
Python 3.6+

Installation

Installing from PyPI

The simplest way to install the Xcode Diagnostics MCP plugin:

pip install mcp-xcode-diagnostics

Installing from GitHub

You can install directly from GitHub:

pip install git+https://github.com/leftspin/mcp-xcode-diagnostics.git

Installing from source

To install from source:

Clone or download this repository
Install the plugin using pip:
cd mcp-xcode-diagnostics pip install .

The plugin can now be used with any MCP-compatible client.

Features

Lists all Xcode projects that have build logs in DerivedData
Extracts errors and warnings from the latest build log of a specific project
Parses complex diagnostics, including associated notes and fix-it suggestions
Provides detailed information about each issue, including file paths, line numbers, and error messages
Optimized for capturing Swift concurrency-related warnings

Supported Diagnostic Types

The plugin can detect and display various types of Xcode diagnostics including:

Errors

Syntax errors (e.g., "expected '{'" or "expected expression")
Type errors (e.g., "cannot convert value of type X to expected argument type Y")
Unresolved identifiers and missing imports
Protocol conformance errors
Generic parameter inference failures
Access control violations

Warnings

Unused variables, constants, and results
Implicit conversions that may lose precision
Redundant code or unnecessary expressions
Deprecation warnings
String interpolation issues
Swift concurrency warnings, including:
- Non-isolated global shared mutable state warnings
- Main actor isolation warnings
- Protocol conformance concurrency warnings
- Actor isolation violations
- Swift 6 language mode compatibility warnings

Notes and Fix-it Suggestions

Associated notes that provide additional context for errors and warnings
Fix-it suggestions that propose code changes to resolve issues
Code snippets showing the problematic code

Limitations

Binary/serialized formats in runtime logs may not be fully parsed
Some highly specialized diagnostic formats may not be recognized
Very large build logs may be truncated
Project-specific custom diagnostics might not be properly categorized

MCP Tools

The plugin provides two main MCP tools:

get_xcode_projects

Lists all Xcode projects with build logs in the DerivedData directory.

Parameters: None

get_project_diagnostics

Gets diagnostic information from the latest build log of a specific project.

Parameters:

project_dir_name: Directory name of the project in DerivedData (e.g., 'ProjectName-hash')
include_warnings: Whether to include warnings in addition to errors (default: True)

Debug Information

For debugging purposes, the plugin saves raw log output to:

/tmp/xcode-mcp-debug.log - Main application logs
/tmp/xcode-diagnostic-raw.log - Raw output from Xcode activity logs

Example Output

{
  "success": true,
  "log_file": "/path/to/build.xcactivitylog",
  "timestamp": "2025-03-11T12:34:56.789",
  "errors": [
    {
      "type": "error",
      "message": "use of unresolved identifier 'NonExistentType'",
      "file_path": "/path/to/MyFile.swift",
      "line_number": 42,
      "column": 15,
      "code": "    let x: NonExistentType = value",
      "notes": []
    }
  ],
  "warnings": [
    {
      "type": "warning",
      "message": "static property 'sharedInstance' is not concurrency-safe because it is nonisolated global shared mutable state; this is an error in the Swift 6 language mode",
      "file_path": "/path/to/SharedManager.swift",
      "line_number": 10,
      "column": 16,
      "code": "    static var sharedInstance: SharedManager?",
      "notes": [
        {
          "type": "note",
          "message": "convert 'sharedInstance' to a 'let' constant to make 'Sendable' shared state immutable",
          "file_path": "/path/to/SharedManager.swift",
          "line_number": 10,
          "column": 16
        }
      ]
    }
  ],
  "error_count": 1,
  "warning_count": 1
}

Testing

The plugin includes a test suite to verify parsing functionality:

# Run all tests
python -m unittest test_xcode_diagnostics.py

License

This project is available under the MIT License.

Integrations