https://github.com/domdomegg/mcp-90-mre

https://github.com/domdomegg/mcp-90-mre

Last synced: 8 months ago
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• Host: GitHub
• URL: https://github.com/domdomegg/mcp-90-mre
• Owner: domdomegg
• License: mit
• Created: 2024-12-13T14:58:03.000Z (11 months ago)
• Default Branch: master
• Last Pushed: 2025-01-22T06:34:45.000Z (10 months ago)
• Last Synced: 2025-01-22T07:32:31.944Z (10 months ago)
• Language: JavaScript
• Size: 104 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

• awesome-mcp-servers - **mcp-90-mre** - 🐛 Minimal repro of a bug with Claude Desktop's MCP integration `javascript` `mcp` `npm install domdomegg/mcp-90-mre` (🌐 Web Development)

README

          
# mcp-90-mre

A minimal Model Context Protocol server that replicates a bug with the Claude Desktop app's MCP implementation. Specifically, using `allOf` or `anyOf` with an object doesn't appear to work correctly.

Also see [discussion #90 on the model context protocol](https://github.com/orgs/modelcontextprotocol/discussions/90).

https://github.com/user-attachments/assets/e22b0d06-f463-4c74-a081-cb0a631cb5e9

## Usage

To use this server with the Claude Desktop app, first clone this repository, install deps (with `npm install`) and build the repo (with `npm run build`).

Then, add the following configuration to the "mcpServers" section of your `claude_desktop_config.json`:

```json

{

  "mcpServers": {

    "postgres": {

      "command": "node",

      "args": [

        "/path/to/mcp-90-mre/dist/index.js"

      ]

    }

  }

}

```

## Components

### Tools

- **format_hello** (Currently not working)

  - Format a hello message

  - Input parameters:

    - `obj`: `allOf`:

      - Base object with `timeOfDay` (string)

      - Either:

        - Group type: `{ type: "group", people: string[] }`

        - Individual type: `{ type: "individual", person: string }`

- **format_goodbye** (Currently not working)

  - Format a goodbye message

  - Input parameters:

    - `obj`: `anyOf`:

      - Group type: `{ timeOfDay: string, type: "group", people: string[] }`

      - Individual type: `{ timeOfDay: string, type: "individual", person: string }`

- **format_sorry** (Working)

  - Format a sorry message

  - Uses a nested object containing a union, which appears to work correctly

  - Input parameters:

    - `obj`: Object containing:

      - `nested`: `anyOf`:

        - Group type: `{ timeOfDay: string, type: "group", people: string[] }`

        - Individual type: `{ timeOfDay: string, type: "individual", person: string }`

## Bug Description

The server implements three different approaches to combining object types:

1. `format_hello` uses `allOf` to combine a base object with a discriminated union

2. `format_goodbye` uses a direct union of complete objects

3. `format_sorry` uses a nested object containing a union

Currently, only the third approach (`format_sorry`) works correctly in the Claude Desktop app. Both `format_hello` and `format_goodbye` fail to validate input properly, suggesting an issue with how the Claude Desktop app handles certain JSON Schema constructs.

## Contributing

Pull requests are welcomed on GitHub! To get started:

1. Install Git and Node.js

2. Clone the repository

3. Install dependencies with `npm install`

4. Run `npm run test` to run tests

5. Build with `npm run build`

  - You can use `npm run build:watch` to automatically build after editing [`src/index.ts`](./src/index.ts). This means you can hit save, reload Claude Desktop (with Ctrl/Cmd+R), and the changes apply.