Duplicate description on schemas used in parameters

src/create/parameters.test.ts

@@ -228,4 +228,43 @@ describe('createParametersObject', () => {
 
     expect(result).toStrictEqual(expectedResult);
   });
+
+  it('should extract the description from the underlying schema', () => {
+    const expectedResult: oas31.BaseParameterObject = {
+      schema: {
+        type: 'string',
+        description: 'foo',
+      },
+      description: 'foo',
+      required: true,
+    };
+    const result = createBaseParameter(
+      z.string().describe('foo'),
+      getDefaultComponents(),
+      ['query'],
+    );
+
+    expect(result).toStrictEqual(expectedResult);
+  });
+
+  it('should allow overriding the description using .openapi.param in the underlying schema', () => {
+    const expectedResult: oas31.BaseParameterObject = {
+      schema: {
+        type: 'string',
+        description: 'foo',
+      },
+      description: 'boo',
+      required: true,
+    };
+    const result = createBaseParameter(
+      z
+        .string()
+        .describe('foo')
+        .openapi({ param: { description: 'boo' } }),
+      getDefaultComponents(),
+      ['query'],
+    );
+
+    expect(result).toStrictEqual(expectedResult);
+  });
 });

src/create/parameters.ts

@@ -28,7 +28,11 @@ export const createBaseParameter = (
     'schema',
   ]);
   const required = !isOptionalSchema(schema, state);
+  const description =
+    schema._def.openapi?.description ?? schema._def.description;
+
   return {
+    ...(description && { description }),
     ...rest,
     ...(schema && { schema: schemaObject }),
     ...(required && { required }),