apc-mcp

apc-mcp is a Model Context Protocol server for audio plugin development. It wraps the tools you already use — CMake, ctest, clang-format, pluginval, clap-validator — into a clean MCP tool interface for building, testing, linting, validating, and scaffolding plugin projects across JUCE, CLAP, VST3, and ARA formats.

Works with any MCP client: Claude Code, OpenCode, VS Code with MCP, Continue.dev, and more.

Quick Start

Add one entry to your MCP config — no npm, no clone, no setup:

{
  "mcp": {
    "apc-mcp": {
      "type": "local",
      "command": ["npx", "-y", "github:sgm-audio/apc-mcp"],
      "enabled": true
    }
  }
}

That's it. npx handles fetching and caching. Updates automatically when you restart your client.

Requirements

• Node.js 18+

• CMake 3.22+ — required for build/configure tools

• clang-format — required for lint tool

• pluginval — required for VST3 validation

• clap-validator — required for CLAP validation

• A JUCE/CLAP/VST3 audio plugin project with a plugins/ directory

Related MCP server: REAPER MCP Server

Tools

Build

audio_plugin_build()
audio_plugin_build(config="Release", clean=true)
audio_plugin_build(projectPath="/path/to/project", target="MyPlugin_Standalone")

Returns structured output with error count, warning count, and the first 20 of each.

Configure

audio_plugin_configure(generator="Ninja")
audio_plugin_configure(options="-DAPC_ENABLE_VISAGE=ON")

Test

audio_plugin_test()
audio_plugin_test(config="Release", testName="MyPluginTest")

Returns pass/failed/total summary.

Lint

audio_plugin_lint()
audio_plugin_lint(fix=true)
audio_plugin_lint(target="plugins/Foo/Source")

Dry-run by default. Pass fix=true to format in place.

List plugins

audio_plugin_plugins(format="json")

Omitting format returns human-readable text. Use format="json" for programmatic consumption.

Validate

audio_plugin_validate()
audio_plugin_validate(format="VST3")
audio_plugin_validate(format="CLAP")

Scans the build directory for plugin binaries and runs the appropriate validator on each.

Scaffold

audio_plugin_create(name="Phaser9000", type="clap")
audio_plugin_create(name="MyVerb", type="juce", vendor="MyCompany", formats="VST3;AU")
audio_plugin_create(name="SimpleDelay", type="clap", vendor="MyCompany", description="A simple delay effect")

Generates a working plugin stub with CMakeLists.txt, source files, and proper CLAP entry point or JUCE AudioProcessor structure.

Configuration

Per-project config

Drop an apc-mcp.json in your project root. When this file is present, projectPath is optional — the server detects your project from the working directory.

{
  "generator": "Ninja",
  "config": "Release",
  "buildDir": "build",
  "pluginsDir": "plugins",
  "validateFormats": ["VST3", "CLAP"],
  "validateCommand": "pluginval",
  "clapValidatorCommand": "clap-validator"
}

Expected layout

my-plugin/
├── apc-mcp.json             # Per-project config (optional)
├── CMakeLists.txt           # Root CMake project
├── plugins/
│   ├── MyPlugin/
│   │   ├── CMakeLists.txt   # Per-plugin CMake target
│   │   ├── Source/
│   │   └── status.json      # Optional metadata (type, version, etc.)
│   └── ...
├── common/                  # Shared sources (optional)
└── build/                   # Build directory (auto-created)

Development

git clone https://github.com/sgm-audio/apc-mcp.git
cd apc-mcp
npm install
npm test          # 11 tests, node:test, zero deps
npm run lint      # syntax check on the server code itself

Project structure

apc-mcp/
├── index.js                    # MCP server — single file, 7 tools
├── templates/
│   ├── clap/                   # CLAP plugin scaffold template
│   └── juce/                   # JUCE plugin scaffold template
├── tests/
│   └── server.test.js          # 11 integration tests
├── .github/
│   ├── workflows/
│   │   ├── publish.yml         # CI: test on push/PR, publish on tag
│   │   └── codeql.yml          # CodeQL security analysis
│   ├── dependabot.yml          # Automated dependency updates
│   └── ISSUE_TEMPLATE/         # Bug report + feature request templates
├── .editorconfig               # Editor consistency
├── CHANGELOG.md
├── CONTRIBUTING.md
└── LICENSE

Versioning

This project follows Semantic Versioning. Breaking changes to any tool's input schema or output format increment the major version.

FAQ / Troubleshooting

Q: I get "command not found: cmake"
A: apc-mcp uses your system's existing toolchain. Install CMake via your package manager: brew install cmake, apt install cmake, or download from cmake.org.

Q: Does it work with VS Code / Cursor / Continue.dev?
A: Yes — any MCP client works. Point it at npx github:sgm-audio/apc-mcp using whatever MCP config format that client uses.

Q: How do I update to a new version?
A: If using npx github:..., clear the npx cache: npx --cache clear github:sgm-audio/apc-mcp — or just restart your MCP client, npx checks for updates automatically.

Q: Can I use this with non-JUCE projects?
A: Yes. audio_plugin_build, audio_plugin_configure, audio_plugin_test, and audio_plugin_lint work with any CMake-based C++ project. Only audio_plugin_create and audio_plugin_validate are plugin-format-specific.

License

MIT © 2026 Scott Mills. See LICENSE.