json-toolkit-mcp

JSON toolkit MCP server. Validate, format, convert, and merge JSON data.

No external dependencies. Pure JSON processing.

Install

npm install -g json-toolkit-mcp

Usage

Claude Desktop / Cursor / OpenCode

Add to your MCP config:

{
  "mcpServers": {
    "json-toolkit": {
      "command": "npx",
      "args": ["-y", "json-toolkit-mcp"]
    }
  }
}

Tools

validate_json — Validate JSON

Validate a JSON string and return error location if invalid.

Input:

{
  "json_string": "{\"name\": \"test\", \"age\": 25}"
}

Output (valid):

{
  "valid": true
}

Output (invalid):

{
  "valid": false,
  "error": {
    "line": 1,
    "column": 17,
    "message": "Unexpected token } in JSON at position 16"
  }
}

format_json — Format JSON

Format a JSON string as pretty-printed or minified.

Input:

{
  "json_string": "{\"a\":1,\"b\":2}",
  "mode": "pretty"
}

Output:

{
  "a": 1,
  "b": 2
}

json_to_typescript — JSON to TypeScript

Infer and generate TypeScript interface from a JSON string.

Input:

{
  "json_string": "{\"name\": \"test\", \"age\": 25, \"active\": true}",
  "interface_name": "User"
}

Output:

export interface User {
  name: string
  age: number
  active: boolean
}

json_to_csv — JSON to CSV

Convert a JSON array of objects to CSV format.

Input:

{
  "json_array_string": "[{\"name\":\"Alice\",\"age\":30},{\"name\":\"Bob\",\"age\":25}]"
}

Output:

name,age
Alice,30
Bob,25

merge_json — Merge JSON

Deep merge multiple JSON objects. Arrays are concatenated, objects are recursively merged, primitives are overwritten.

Input:

{
  "json_strings": [
    "{\"a\":1,\"b\":{\"x\":1}}",
    "{\"b\":{\"y\":2},\"c\":3}"
  ]
}

Output:

{
  "a": 1,
  "b": {
    "x": 1,
    "y": 2
  },
  "c": 3
}

Design

| Feature | Why | |---------|-----| | Zero runtime deps | Only @modelcontextprotocol/sdk and zod | | Pure JSON processing | No external libraries needed | | TypeScript inference | Auto-generate interfaces from JSON data | | Deep merge | Recursive object merging with array concatenation | | CSV conversion | Handles nested objects with dot notation flattening |

License

MIT