fix(catalog-mcp): create-product could never succeed

The tool's request schema omitted productcode, which catalog-api requires
(ProductRequest in openapi.yaml lists it among the eight required fields).
Since the declared schema is the only thing an MCP caller sees, there was no
input that worked: omit it and the API answers
{"productcode":["This field is required."]}; supply it and ai-mcp-proxy rejects
the call first with "Additional properties are not allowed ('productcode' was
unexpected)".

The schema now mirrors ProductRequest — productcode added, the same eight
fields marked required, and the length and format constraints carried over so
a model reads them rather than guessing.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

kong/mcp/ai-mcp-proxy.yaml

@@ -72,25 +72,50 @@ config:
         required: true
         content:
           application/json:
+            # Mirrors ProductRequest in catalog-api/openapi.yaml. It has to:
+            # this schema is the only thing the caller sees, so anything it
+            # omits the caller cannot send. `productcode` was missing and is
+            # required by the API, which made this tool impossible to call
+            # successfully — every attempt came back
+            # {"productcode":["This field is required."]}, and a caller that
+            # tried to supply it anyway was rejected earlier still, here.
             schema:
               type: object
               properties:
+                productcode:
+                  type: string
+                  maxLength: 15
+                  description: Unique catalog identifier, e.g. S10_1949. Ask for it; do not invent one.
                 productname:
                   type: string
+                  maxLength: 70
                 productline:
                   type: string
+                  description: Must be an existing product line, as returned by list-productlines.
                 productscale:
                   type: string
+                  maxLength: 10
                 productvendor:
                   type: string
+                  maxLength: 50
                 productdescription:
                   type: string
                 quantityinstock:
                   type: integer
+                  minimum: -32768
+                  maximum: 32767
                 buyprice:
                   type: string
+                  description: Decimal as a string, at most two places, e.g. "50.00".
                 msrp:
                   type: string
+                  description: Decimal as a string, at most two places, e.g. "99.00".
               required:
+                - productcode
                 - productname
                 - productline
+                - productscale
+                - productvendor
+                - productdescription
+                - buyprice
+                - msrp