SimplePostTool: FATAL: Solr returned an error #400 Bad Request

Probable reasons :

1. What ever you are trying to post has wrong entries that does not match with the solr schema. it can be
1. Value Type
2. Value not found if it is required field
3. Value format is not correct

Solution :

1. Check the solr log for porper error
2. make your posting data in correct format
3. check for the field type which you are posting.