Dynamic Field Values won't load

I am working on a custom email integration that will send mail using a user-specified template. I need to build an automation that lets the user select a mail body template:

However, my issue is the list of templates never loads from my URL. If I hit the URL in postman, I get a result like this:

[
    {
        "id": 1,
        "title": "Test",
        "outboundType": "text",
        "inboundTypes": [
            "text"
        ]
    },
    {
        "id": 2,
        "title": "Test 2",
        "outboundType": "text",
        "inboundTypes": [
            "text"
        ]
    }
]

It also sometimes says “failed to load”. I am looking for guidance on how to debug this as the error appears to be deep within Monday. It appears to be returning error 500 if I check devtools, but this is an error from Monday’s API which is in turn calling mine:

It turns out that Monday uses POST instead of GET. I don’t think this is very well documented, but after switching my endpoint to POST it all works as expected.

Hello!
The template list in your custom email integration isn’t loading from the provided URL. This could be due to network access issues preventing the automation from reaching the URL, an incorrect URL or HTTP method being used, missing required headers or authentication details in the automation’s request, or a problem with how the automation is processing the JSON response. Checking the URL’s accessibility, verifying the request details in your automation against your successful Postman test, and reviewing any error messages from your automation will help diagnose the problem. centura health login