POST RequestBody schema(OPENAPI 3)

So I'm trying a create a spec(YAML) file for my Restservice. In requestbody I'm expecting a complex JSON with many fields. Now in Spec file how exactly the requestbody's schema, properties should be(defining every property of complex JSON will be too cumbersome)? Can I define requestbody of the schema as an object or array that will then handle the complete JSON object itself.