CRM Custom Module API

CRM Custom Module API

Hi!
I need to insert record into custom module 

i make API POST:
https://crm.zoho.com/crm/private/xml/CustomModule1/insertRecords?authtoken=...&scope=crmapi
Content-Type:
application/x-www-form-urlencoded; charset=UTF-8
Body o request :
xmlData=<CustomModule1><row no="1"><FL val="Objekt Name">qwertyui</FL></row> </CustomModule1>
(parameter urlencoded)

i got response 
<response uri="/crm/private/xml/CustomModule1/insertRecords">
  <error>
    <code>4401</code>
    <message>Unable to populate data, please check if mandatory value is entered correctly.</message>
  </error>
</response>

Does it mean that CRM API doesn't allow to insert records in custom module ?