Mcp Server Diff

# MCP Server Diff

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A GitHub Action for diffing [Model Context Protocol (MCP)](https://modelcontextprotocol.io/) server **public interfaces** between versions. Compares the current branch against a baseline to surface any changes to your server's exposed tools, resources, prompts, and capabilities.

> **Also available as a standalone CLI** — see [CLI Documentation](#cli-tool) or install with `npx mcp-server-diff`

## Overview

MCP servers expose a **public interface** to AI assistants: tools (with their input schemas), resources, prompts, and server capabilities. As your server evolves, changes to this interface are worth tracking. This action automates public interface comparison by:

1. Building your MCP server from both the current branch and a baseline (merge-base, tag, or specified ref)
2. Querying both versions for their complete public interface (tools, resources, prompts, capabilities)
3. Generating a diff report showing exactly what changed
4. Surfacing results directly in GitHub's Job Summary

This is **not** about testing internal logic or correctness—it's about visibility into what your server _advertises_ to clients.

## Quick Start

Create `.github/workflows/mcp-diff.yml` in your repository:

```yaml
name: MCP Server Diff

on:
  pull_request:
    branches: [main]
  push:
    branches: [main]
    tags: ['v*']

permissions:
  contents: read

jobs:
  mcp-diff:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - uses: SamMorrowDrums/mcp-server-diff@v2
        with:
          setup_node: true
          install_command: npm ci
          build_command: npm run build
          start_command: node dist/stdio.js
```

## Language Examples

### Node.js / TypeScript

```yaml
- uses: SamMorrowDrums/mcp-server-diff@v2
  with:
    setup_node: true
    node_version: '22'
    install_command: npm ci
    build_command: npm run build
    start_command: node dist/stdio.js
```

### Python

```yaml
- uses: SamMorrowDrums/mcp-server-diff@v2
  with:
    setup_python: true
    python_version: '3.12'
    install_command: pip install -e .
    start_command: python -m my_mcp_server
```

### Go

```yaml
- uses: SamMorrowDrums/mcp-server-diff@v2
  with:
    setup_go: true
    install_command: go mod download
    build_command: go build -o bin/server ./cmd/stdio
    start_command: ./bin/server
```

### Rust

```yaml
- uses: SamMorrowDrums/mcp-server-diff@v2
  with:
    setup_rus

... [View full README on GitHub]