diff --git a/src/jsonSchema.ts b/src/jsonSchema.ts
new file mode 100644
index 0000000..c0773ad
--- /dev/null
+++ b/src/jsonSchema.ts
@@ -0,0 +1,9 @@
+import type { ObjectSchema, Schema } from './types'
+
+export function jsonSchema(schema: Schema): ObjectSchema {
+  if (schema.type !== 'object') {
+    throw new Error('Top-level schema must be an object')
+  }
+
+  return schema
+}