MCP. How setup description for each field?

[DudeFactory]

What is the correct way to register the tool so that each field description appears in the MCP inputSchema?

Is .shape the problem, or is there a known limitation in Zod → JSON Schema conversion in MCP?

tools/list, the generated inputSchema only shows:
"imageData": { "type": "string" }

"@payloadcms/plugin-mcp": "3.76.0",
"zod": "^4.3.5"

I’m defining an MCP tool in Payload CMS using Zod with .describe() on each field:

const uploadImageParams = z.object({
  imageData: z.string().describe('Base64 encoded image data. Can include data URI prefix.'),
  title: z.string().describe('SEO-friendly title for the image, used for filename generation.'),
  alt: z.string().describe('Alt text for accessibility, describing the image content.'),
  description: z.string().optional().describe('Optional description or caption for the image.'),
  mimeType: z
    .string()
    .optional()
    .describe(
      'MIME type of the image (e.g., "image/jpeg"). If not provided, it will be auto-detected.',
    ),
})

export const uploadImage = {
  name: 'uploadImage',
  description:
    'Upload a base64-encoded image to the Media collection. Automatically compresses images larger than 500KB to optimize file size while maintaining quality. Returns the uploaded media document with URL, ID, and metadata. Requires: imageData (base64 string), title (for filename generation), and alt (for accessibility).',
  parameters: uploadImageParams.shape,
  handler: async (params: any, reqOrExtra?: any, extra?: any) => {
    
  },
}