If you are one of the unlucky ones in need of working with Insightly API, you have probably noticed there’s no way to create a TAG under Contact endpoint.

If you follow the documentation, you probably do a CURL request similar to this:

        $username = 'xxxxx'; // api key
        $ch = curl_init('https://api.insightly.com/v3.0/Contacts/');

        curl_setopt($ch, CURLOPT_HTTPHEADER, [
            'Content-Type: application/json',
            'Authorization: Basic '. base64_encode($username)
        ]);

        $dataString = json_encode(array(
            'FIRST_NAME' => 'First',
            'LAST_NAME' => 'Last',
            'EMAIL_ADDRESS' => 'test@test.sk',
            "TAGS" => array(
                array("TAG_NAME" => "TEST")
            )
        ));

        curl_setopt($ch, CURLOPT_POST, 1);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $dataString);
        curl_setopt($ch , CURLOPT_HEADER, 1);
        curl_setopt($ch , CURLOPT_TIMEOUT, 30);
        curl_setopt($ch , CURLOPT_RETURNTRANSFER, TRUE);
        $return = curl_exec($ch );

        $header_size = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
        $header = substr($return, 0, $header_size);
        $body = substr($return, $header_size);

And all you get in return is 400 Bad Request!
Even if you try to update existing Contact using https://api.insightly.com/v3.0/Contacts/{ID}/Tags endoing you won’t have any more luck.

The solution is simple – go back to 2.3 endpoints – the exact same post data works on 2.3!

Insightly has done a really poor job on their API ..

Bottom line – change https://api.insightly.com/v3.0/Contacts/ to https://api.insight.ly/v2.3/Contacts/