diff --git a/scripts/notion-openapi.json b/scripts/notion-openapi.json
index 8fa15770..0aa56cbd 100644
--- a/scripts/notion-openapi.json
+++ b/scripts/notion-openapi.json
@@ -1513,6 +1513,11 @@
         "summary": "Create comment",
         "description": "Creates a comment in a page or existing discussion thread.",
         "operationId": "create-a-comment",
+        "parameters": [
+          {
+            "$ref": "#/components/parameters/notionVersion"
+          }
+        ],
         "requestBody": {
           "content": {
             "application/json": {
diff --git a/src/openapi-mcp-server/openapi/__tests__/notion-version-coverage.test.ts b/src/openapi-mcp-server/openapi/__tests__/notion-version-coverage.test.ts
new file mode 100644
index 00000000..ab26f21b
--- /dev/null
+++ b/src/openapi-mcp-server/openapi/__tests__/notion-version-coverage.test.ts
@@ -0,0 +1,43 @@
+import fs from 'node:fs'
+import path from 'node:path'
+import { describe, expect, it } from 'vitest'
+import type { OpenAPIV3 } from 'openapi-types'
+
+/**
+ * Every Notion API operation must declare the shared Notion-Version header
+ * parameter so HttpClient.buildDefaultHeaders() can attach the version.
+ */
+describe('Notion OpenAPI spec Notion-Version coverage', () => {
+  const spec = JSON.parse(
+    fs.readFileSync(path.resolve(process.cwd(), 'scripts/notion-openapi.json'), 'utf-8'),
+  ) as OpenAPIV3.Document
+
+  const notionVersionRef = '#/components/parameters/notionVersion'
+
+  function hasNotionVersionParameter(operation: OpenAPIV3.OperationObject): boolean {
+    return (operation.parameters ?? []).some((param) => {
+      if ('$ref' in param) {
+        return param.$ref === notionVersionRef
+      }
+      return param.in === 'header' && param.name === 'Notion-Version'
+    })
+  }
+
+  it('declares Notion-Version on every operation', () => {
+    const missing: string[] = []
+
+    for (const [pathKey, pathItem] of Object.entries(spec.paths ?? {})) {
+      for (const method of ['get', 'post', 'put', 'patch', 'delete'] as const) {
+        const operation = pathItem?.[method]
+        if (!operation?.operationId) {
+          continue
+        }
+        if (!hasNotionVersionParameter(operation)) {
+          missing.push(`${method.toUpperCase()} ${pathKey} (${operation.operationId})`)
+        }
+      }
+    }
+
+    expect(missing).toEqual([])
+  })
+})