Figma MCP response sees not follow the spec (old specification version)

When initailizing, the Figma local mcp server resopnse in serverInfo with things like:

{
      "protocolVersion": "2025-06-18",
      "capabilities": {
        "tools": {
          "listChanged": true
        },
        "resources": {
          "listChanged": true,
          "subscribe": true
        },
        "prompts": {
          "listChanged": true
        }
      },
      "serverInfo": {
        "name": "Figma MCP Server",
        "version": "1.0.0"
        // ... 
        "icons": {
           "src": "...",
           "sizes": "128x160" <======== look at here
       // ...

The “sizes” return a  string, which in the old draft version it should be string[], see here:
https://modelcontextprotocol.io/specification/draft/schema#icon

And this makes clients like codex don’t work, since codex depends on https://github.com/modelcontextprotocol/rust-sdk , which recently add support for this field