Guide: Enable Draft 2020-12 schema support for MCP in VS Code

[azwri]

JSON Schema Draft 2020-12 Support for MCP Configuration in VS Code

Issue

When using the Firecrawl MCP server configuration in VS Code, the built-in JSON validator shows warnings about unsupported Draft 2020-12 schema features. This is because VS Code's built-in validator doesn't fully support JSON Schema Draft 2020-12.

Solution

Here's how to enable proper Draft 2020-12 support in VS Code for your MCP configuration:

1. Install Extension

JSON Schema Diagnostics

• Open Extensions (Ctrl+Shift+X)
• Search: prosser.json-schema-2020-validation
• Click Install

2. Configure Workspace Settings

Create or update .vscode/settings.json in your workspace:

{
  "json.schemas": [
    {
      "fileMatch": ["**/mcp.json"],
      "url": "https://github.com/modelcontextprotocol/specification/raw/main/schema/mcp.json"
    }
  ],
  "json.validate.enable": false
}

Important: json.validate.enable: false disables the built-in validator to prevent false warnings. The installed extension handles validation properly.

3. Example MCP Configuration

Your mcp.json should work without warnings:

{
  "$schema": "https://github.com/modelcontextprotocol/specification/raw/main/schema/mcp.json",
  "servers": {
    "firecrawl-mcp": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "firecrawl-mcp"],
      "env": {
        "FIRECRAWL_API_KEY": "YOUR_API_KEY"
      }
    }
  },
  "inputs": []
}

Results

✅ IntelliSense works correctly
✅ No warnings about unsupported schema features
✅ Real-time validation against MCP schema
✅ Proper autocomplete for Firecrawl MCP configuration

Troubleshooting

No IntelliSense? Reload VS Code window (Ctrl+Shift+P → "Developer: Reload Window")

Still seeing warnings? Verify json.validate.enable: false in your settings

Additional Context

• Extension: JSON Schema Diagnostics
• MCP Specification: Model Context Protocol
• Draft 2020-12 Spec: JSON Schema 2020-12

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This setup improves the developer experience when configuring Firecrawl MCP servers in VS Code.

[jimfm]

Thank you, this worked perfectly as a workaround to fix the issue.

[donz0]

Works but the extension outputs errors prosser/json-schema-validation-extension#11 (comment)