JSONPlaceholder MCP Server

This is a Model Context Protocol (MCP) server that provides tools to interact with the JSONPlaceholder API.

Features

The server provides tools for all JSONPlaceholder endpoints:

Posts: get_posts, get_post, create_post, update_post, delete_post
Comments: get_comments, get_comment, create_comment, update_comment, delete_comment
Albums: get_albums, get_album, create_album, update_album, delete_album
Photos: get_photos, get_photo, create_photo, update_photo, delete_photo
Todos: get_todos, get_todo, create_todo, update_todo, delete_todo
Users: get_users, get_user, create_user, update_user, delete_user

Installation

Clone this repository:

git clone <repository-url>
cd jsonplaceholder-mcp-server

Install dependencies:
```
npm install
```
Build the server:
```
npm run build
```
This bundles the server with esbuild into the build/ folder.

Start the server:

npm start

You should see:

JSONPlaceholder MCP server running on stdio

Usage

The server uses stdio transport, which means it can communicate with any MCP client that supports stdio.
Common MCP clients include:
- VS Code MCP extension (for debugging and testing tools)
- Claude Desktop

Connecting in an MCP Client

Open your MCP client (VS Code, Claude, etc.)
Configure it to use a custom MCP server with stdio transport.
Point the client to the server you just started (npm start).

All tools (posts, comments, albums, photos, todos, users) will now be available in the client.

Testing

The project includes a comprehensive test suite to verify all MCP tools are working correctly. Tests use JSON RPC communication to interact with the server.

Running Tests

Run All Tests

npm test

Run Individual Test Suites

# Test specific tool categories
npm run test:users      # Test user-related tools
npm run test:posts      # Test post-related tools
npm run test:comments   # Test comment-related tools
npm run test:albums     # Test album-related tools
npm run test:photos     # Test photo-related tools
npm run test:todos      # Test todo-related tools

Run Tests Directly

# Run individual test files
node tests/users.test.js
node tests/posts.test.js
node tests/comments.test.js
node tests/albums.test.js
node tests/photos.test.js
node tests/todos.test.js

# Run the main test runner
node tests/tests.js

Test Structure

The test suite is organized into separate files for each tool category:

tests/
├── testHelper.js          # Shared MCP testing utilities
├── tests.js              # Main test runner (runs all tests)
├── users.test.js         # Users tool tests (5 tests)
├── posts.test.js         # Posts tool tests (6 tests)
├── comments.test.js      # Comments tool tests (6 tests)
├── albums.test.js        # Albums tool tests (6 tests)
├── photos.test.js        # Photos tool tests (6 tests)
└── todos.test.js         # Todos tool tests (6 tests)

Test Coverage

Each tool category includes tests for:

GET all items (e.g., get_users, get_posts)
GET filtered items (e.g., get_posts?userId=1, get_comments?postId=1)
GET single item (e.g., get_user, get_post)
CREATE new item (e.g., create_user, create_post)
UPDATE existing item (e.g., update_user, update_post)
DELETE item (e.g., delete_user, delete_post)

Total: 35 individual tests across 6 test suites

Test Output

When tests pass, you'll see:

==================================================
Running Users Tests
==================================================

Starting Users Tests...
JSONPlaceholder MCP server running on stdio
Testing get_users with args: {}
✓ get_users succeeded: [...]

Users Tests Results: 5 passed, 0 failed
✅ Users tests: PASSED

Debugging Tests

If tests fail, the output will show:

Which specific test failed
Error messages from the MCP server
Individual test results for each suite

You can run individual test suites to isolate issues:

npm run test:users  # Only run user tests

API Reference

All tools follow REST-like conventions and interact with the JSONPlaceholder API.
Note: JSONPlaceholder is a fake API; create/update/delete operations return mock responses but do not persist data.

Development

Project Structure

├── index.js              # Main server entry point
├── build/index.js        # Bundled server (generated)
├── tools/                # Individual tool implementations
│   ├── users.js
│   ├── posts.js
│   ├── comments.js
│   ├── albums.js
│   ├── photos.js
│   └── todos.js
├── tests/                # Test suite
│   ├── testHelper.js     # Shared testing utilities
│   ├── tests.js         # Main test runner
│   └── *.test.js        # Individual test files
├── package.json
└── README.md

Available Scripts

npm run build - Bundle the server with esbuild
npm start - Start the MCP server
npm test - Run all tests
npm run test:* - Run specific test suites

VS Code Development

This project includes VS Code configurations for easy development and debugging:

Launch Configurations

The .vscode/launch.json file provides several run/debug configurations:

Run MCP Server (Development): Runs the server from source code (index.js)
Run MCP Server (Production): Runs the built server (build/index.js)
Debug MCP Server: Debug the server with breakpoints and inspection
Run Tests: Run the test suite with debugging capabilities

Tasks

The .vscode/tasks.json file provides build tasks:

Build MCP Server: Builds the project using npm run build
Run Tests: Runs all tests using npm test
Install Dependencies: Installs npm dependencies
Clean Build: Removes the build directory

How to Use

Running the Server:
- Open the Run and Debug panel (Ctrl+Shift+D / Cmd+Shift+D)
- Select "Run MCP Server (Development)" from the dropdown
- Click the green play button or press F5
Debugging:
- Set breakpoints in your code
- Select "Debug MCP Server" configuration
- Run with F5 - the server will start and you can debug with breakpoints
Running Tests:
- Select "Run Tests" from the launch configurations
- Or use Ctrl+Shift+P → "Tasks: Run Task" → "Run Tests"
Building:
- Use Ctrl+Shift+P → "Tasks: Run Build Task" → "Build MCP Server"
- Or use the terminal: npm run build

MCP Configuration

The .vscode/mcp.json file configures the MCP server for VS Code's MCP extension:

{
  "servers": {
    "jsonplaceholder-server": {
      "type": "stdio",
      "command": "node",
      "args": ["build/index.js"]
    }
  }
}

MCP SDK

This project uses the Model Context Protocol SDK for Node.js.

MCP Servers