scripted restAPI for attachment API

[Anuja111]

My requirement is I want to upload /attach the file to an incident using rest API. A third party can upload the file and it will attach to the incident. using scripted REST API, I don't want the OOB attachment rest API to add an attachment to
an incident.
The user should able to upload the file and then automatically it will attach to the incident. 

Any support would be appreciated. 

Thank You 

[Mark Manders]

What is your reason for not wanting to use the OOB REST API? 

How are you uploading these? Is it coming from another system, is it done through the portal, please provide some more information on the process.

[Anuja111]

Hi mark,

So requestors are generating the incident through SNOW API and they are creating incidents from SNOW API it will create an incident in servicenow automatically same thing again when they attach any file through SNOW API then it will automatically attach the attachment to the incident in servicenow.