diff --git a/kong/mcp/ai-mcp-proxy.yaml b/kong/mcp/ai-mcp-proxy.yaml
index 0356590..eabd038 100644
--- a/kong/mcp/ai-mcp-proxy.yaml
+++ b/kong/mcp/ai-mcp-proxy.yaml
@@ -288,7 +288,8 @@ config:
       idempotent_hint: false
       destructive_hint: false
       open_world_hint: false
-    description: Update specific fields of an existing product.
+    description: Update specific fields of an existing product. Send X-Stock-Change-Reason as delivery:<id>
+      when a quantityinstock change is a fulfilled reorder rather than a correction.
     method: PATCH
     name: patch-product
     parameters:
@@ -298,6 +299,13 @@ config:
       required: true
       schema:
         type: string
+    - description: 'Only honoured in this one shape: delivery:<reorder-id>. Anything else is recorded
+        as a manual adjustment.'
+      in: header
+      name: X-Stock-Change-Reason
+      required: false
+      schema:
+        type: string
     path: /catalog/v1/products/{productcode}/
     request_body:
       content:
diff --git a/openapi.yaml b/openapi.yaml
index 41c82cf..5cb2529 100644
--- a/openapi.yaml
+++ b/openapi.yaml
@@ -271,7 +271,7 @@ paths:
   /catalog/v1/products/{productcode}/:
     patch:
       operationId: patch_product
-      description: Update specific fields of an existing product.
+      description: Update specific fields of an existing product. Send X-Stock-Change-Reason as delivery:<id> when a quantityinstock change is a fulfilled reorder rather than a correction.
       summary: Partially update a product
       parameters:
         - in: path
@@ -280,6 +280,13 @@ paths:
             type: string
           description: A unique value identifying this product.
           required: true
+        - in: header
+          name: X-Stock-Change-Reason
+          schema:
+            type: string
+            pattern: '^delivery:[\w-]{1,64}$'
+          description: 'Only honoured in this one shape: delivery:<reorder-id>. Anything else is recorded as a manual adjustment.'
+          required: false
       tags:
         - Products
       requestBody: