Make the Contact create API behave like UI in the way in checks for duplicates
I did some research in the code. When you use the contact API, the default Unsupervised rule for the Contact Type. This rule is configurable in the Contacts -> Find and Merge Duplicate Contacts screen. 

Update: The contact has another option. You can use the duplicatecheck method. But it cannot be tested in the API explorer. The following code returns the contact_ids found deduplication rule 4 (Checking on email for Individuals).

$result = civicrm_api3('Contact', 'duplicatecheck', array(
     'return' =&gt; array("display_name"),
     'dedupe_rule_id' =&gt; 4,
     'check_permission' =&gt; FALSE,
     'match' =&gt; array(
        'contact_type' =&gt; 'Individual',
        'email'        =&gt; 'blue@example.com'
  )
));