Thank you for reaching out to Constant Contact API Developer Support. My team is here to assist outside software developers with questions about building into Constant Contact's API.
Constant Contact provides developers with free access to our V3 API endpoints for developers building their own application for integration. You can get started using our API by visiting our documentation here:
Additionally, you can utilize our API Reference Page to find body schemas & values, as well as test the functionality of our available endpoints to see how they will work once programmed within your application:
When developing your own application for integration, you’ll need to set it up so that the application calls/retrieves the data of your choosing using the your software's API or other data export method (You will need to check their API documentation or contact their support team for help with how to configure this part), then you will program your application to sort out which variables you need and parse them into the correct format for Constant Contact’s API, at which point you can send that data through to the Constant Contact account via an authenticated connection (or vice versa).
While Constant Contact doesn’t offer any services as far as assistance with building custom integrations, and our expertise is with our API itself as opposed to its implementation within any particular programming language, we are happy to answer any questions pertaining to Constant Contact’s API endpoints, functionality, and documentation.
Please have a look and let us know if you have any other questions!