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Contributing to MCP Apps SDK

We welcome contributions to the MCP Apps SDK! This document outlines the process for contributing to the project.

Getting Started

  1. Fork the repository
  2. Clone your fork: git clone https://github.com/YOUR-USERNAME/ext-apps.git
  3. Install dependencies: npm install
  4. Build the project: npm run build
  5. Run tests: npm test

Development Process

  1. Create a new branch for your changes
  2. Make your changes
  3. Run npm run prettier to ensure code style compliance
  4. Run npm test to verify all tests pass
  5. Submit a pull request

Pull Request Guidelines

  • Follow the existing code style
  • Include tests for new functionality
  • Update documentation as needed
  • Keep changes focused and atomic
  • Provide a clear description of changes
  • Keep "Allow edits by maintainers" checked when opening your PR — this lets maintainers rebase your branch and lets the /update-snapshots workflow push updated screenshots to it

Examples Policy

The examples in examples/ are maintained by the core team. We do not accept pull requests that add new example servers from outside contributors. Each example carries an ongoing maintenance cost — keeping it building, tested, and up to date with SDK changes — so we are deliberate about what we add.

If you have an idea for an example that would provide significant educational value, please open an issue describing what the example would demonstrate and why it would be useful, and maintainers will evaluate the request.

PRs that add new examples without a prior approved issue may be closed.

Running Examples

Start the development environment with hot reloading:

npm run examples:dev

Or build and run examples:

npm run examples:start

With MCP Clients

To use these examples with MCP clients that support the stdio transport (such as Claude Desktop or VS Code), add this MCP server configuration to your client's settings:

MCP client configuration for all examples (using stdio) 
{
  "mcpServers": {
    "basic-react": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-basic-react",
        "--stdio"
      ]
    },
    "basic-vanillajs": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-basic-vanillajs",
        "--stdio"
      ]
    },
    "basic-vue": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-basic-vue",
        "--stdio"
      ]
    },
    "basic-svelte": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-basic-svelte",
        "--stdio"
      ]
    },
    "basic-preact": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-basic-preact",
        "--stdio"
      ]
    },
    "basic-solid": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-basic-solid",
        "--stdio"
      ]
    },
    "budget-allocator": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-budget-allocator",
        "--stdio"
      ]
    },
    "cohort-heatmap": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-cohort-heatmap",
        "--stdio"
      ]
    },
    "customer-segmentation": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-customer-segmentation",
        "--stdio"
      ]
    },
    "map": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-map",
        "--stdio"
      ]
    },
    "pdf": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-pdf",
        "--stdio"
      ]
    },
    "scenario-modeler": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-scenario-modeler",
        "--stdio"
      ]
    },
    "shadertoy": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-shadertoy",
        "--stdio"
      ]
    },
    "sheet-music": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-sheet-music",
        "--stdio"
      ]
    },
    "system-monitor": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-system-monitor",
        "--stdio"
      ]
    },
    "threejs": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-threejs",
        "--stdio"
      ]
    },
    "transcript": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-transcript",
        "--stdio"
      ]
    },
    "video-resource": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-video-resource",
        "--stdio"
      ]
    },
    "wiki-explorer": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-wiki-explorer",
        "--stdio"
      ]
    },
    "qr": {
      "command": "uv",
      "args": [
        "run",
        "/path/to/ext-apps/examples/qr-server/server.py",
        "--stdio"
      ]
    },
    "say": {
      "command": "uv",
      "args": [
        "run",
        "--default-index",
        "https://pypi.org/simple",
        "https://raw.githubusercontent.com/modelcontextprotocol/ext-apps/refs/heads/main/examples/say-server/server.py",
        "--stdio"
      ]
    }
  }
}

Note

The qr server requires cloning the repository first. See qr-server README for details.

Local Development

To test local modifications with MCP clients, first clone and install the repository:

git clone https://github.com/modelcontextprotocol/ext-apps.git
cd ext-apps
npm install

Then configure your MCP client to build and run the local server. Replace ~/src/ext-apps with your actual clone path.

Most example servers have a start:stdio script that builds and launches in stdio mode:

MCP client configuration for local development (all examples) 
{
  "mcpServers": {
    "basic-react": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/basic-server-react && npm --silent run start:stdio"
      ]
    },
    "basic-vanillajs": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/basic-server-vanillajs && npm --silent run start:stdio"
      ]
    },
    "basic-vue": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/basic-server-vue && npm --silent run start:stdio"
      ]
    },
    "basic-svelte": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/basic-server-svelte && npm --silent run start:stdio"
      ]
    },
    "basic-preact": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/basic-server-preact && npm --silent run start:stdio"
      ]
    },
    "basic-solid": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/basic-server-solid && npm --silent run start:stdio"
      ]
    },
    "budget-allocator": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/budget-allocator-server && npm --silent run start:stdio"
      ]
    },
    "cohort-heatmap": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/cohort-heatmap-server && npm --silent run start:stdio"
      ]
    },
    "customer-segmentation": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/customer-segmentation-server && npm --silent run start:stdio"
      ]
    },
    "map": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/map-server && npm --silent run start:stdio"
      ]
    },
    "pdf": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/pdf-server && npm --silent run start:stdio"
      ]
    },
    "scenario-modeler": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/scenario-modeler-server && npm --silent run start:stdio"
      ]
    },
    "shadertoy": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/shadertoy-server && npm --silent run start:stdio"
      ]
    },
    "sheet-music": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/sheet-music-server && npm --silent run start:stdio"
      ]
    },
    "system-monitor": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/system-monitor-server && npm --silent run start:stdio"
      ]
    },
    "threejs": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/threejs-server && npm --silent run start:stdio"
      ]
    },
    "transcript": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/transcript-server && npm --silent run start:stdio"
      ]
    },
    "video-resource": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/video-resource-server && npm --silent run start:stdio"
      ]
    },
    "wiki-explorer": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/src/ext-apps/examples/wiki-explorer-server && npm --silent run start:stdio"
      ]
    },
    "qr": {
      "command": "bash",
      "args": [
        "-c",
        "uv run ~/src/ext-apps/examples/qr-server/server.py --stdio"
      ]
    },
    "say": {
      "command": "bash",
      "args": [
        "-c",
        "uv run --index https://pypi.org/simple ~/src/ext-apps/examples/say-server/server.py --stdio"
      ]
    }
  }
}

This configuration rebuilds each server on launch, ensuring your local changes are picked up.

Testing

Unit Tests

Run unit tests with Bun:

npm test

E2E Tests

E2E tests use Playwright to verify all example servers work correctly with screenshot comparisons.

# Run all E2E tests
npm run test:e2e

# Run a specific server's tests
npm run test:e2e -- --grep "Budget Allocator"

# Run tests in interactive UI mode
npm run test:e2e:ui

Updating Golden Screenshots

When UI changes are intentional, update the golden screenshots:

# Update all screenshots
npm run test:e2e:update

# Update screenshots for a specific server
npm run test:e2e:update -- --grep "Three.js"

Note: Golden screenshots are platform-agnostic. Tests use canvas masking and tolerance thresholds to handle minor cross-platform rendering differences.

Updating Snapshots in CI

If E2E tests fail in CI due to screenshot mismatches, you can update snapshots directly from your PR:

  1. Comment /update-snapshots on the PR
  2. The workflow will update snapshots and push to your branch
  3. A comment will confirm when complete

Alternatively, use the workflow dispatch to manually trigger updates for any branch.

Code of Conduct

This project follows our Code of Conduct. Please review it before contributing.

Reporting Issues

  • Use the GitHub issue tracker
  • Search existing issues before creating a new one
  • Provide clear reproduction steps

Security Issues

Please review our Security Policy for reporting security vulnerabilities.

For Maintainers

Repository Setup

This repository uses npm trusted publishing with OIDC - no secrets required.

Before publishing releases, ensure the following are configured:

  1. Trusted publisher on npm: Configure the package to trust this GitHub repository

  2. Release environment (optional): Create a protected environment for additional safeguards

    • Go to Settings > Environments > New environment
    • Name it Release
    • Add required reviewers or other protection rules as needed

Publishing a Release

  1. Bump the version across the root and all workspace packages:

    npm run bump -- minor   # or: patch | major | prerelease --preid=beta | 1.7.0

    Commit and open a PR with a grouped changelog in the body (see prior chore: bump … PRs for the format).

  2. Merge the PR, then draft a GitHub Release — create a vX.Y.Z tag on main, paste the changelog, publish.

  3. Approve the deployment — publishing the Release triggers the npm-publish workflow; all publish jobs wait together for a single "Review deployments" approval.

npm Tags

The workflow automatically determines the npm dist-tag:

Version Pattern npm Tag Install Command
X.Y.Z (from main) latest npm install @modelcontextprotocol/ext-apps
X.Y.Z-beta.N beta npm install @modelcontextprotocol/ext-apps@beta
X.Y.Z (from release branch) release-X.Y npm install @modelcontextprotocol/ext-apps@release-X.Y

Maintenance Releases

To release a patch for an older version:

  1. Create a release branch from the tag: git checkout -b release-0.1 v0.1.0
  2. Cherry-pick or apply fixes
  3. Bump the patch version
  4. Create a GitHub Release targeting the release branch
  5. The package will be published with tag release-0.1

Testing Pre-releases

Every commit and PR automatically publishes a preview package via pkg-pr-new. Check the PR comments or workflow logs for the install command.

License

By contributing, you agree that your contributions will be licensed under the MIT License.