Thank you @wibeasley. My experience was a misunderstanding of what was required for a complete/valid URI. I don't know if all API calls end with or include the string "api", but, if that's the case, perhaps this could be reflected in the documentation and a function to check that the value entered for the redcap_uri ends with or include "api". My error was using only "https://server.org/" rather than "https://server.org/apps/redcap/api/" I was able to identify my error by going to the API Playground section of the RedCap project, which may another resource to call out in the documentation.

1. Sure, I can do that with a regex like ^.+?/api/?$, which wouldn't cost a round trip to the server
2. Maybe it could be a warning (not an error) in case someone is doing something unconventional redirecting paths.
3. Is there anything you'd change/add to redcap_read()'s documentation, and its examples below?

I guess I would more explicitly call out the expected URI syntax in the redcap_uri argument description (i.e. "The URI (uniform resource identifier) of the REDCap project API generally formatted as https://server.org/apps/redcap/api/. Required.") and/or create a more explicitly focused redcap_read example highlighting the expect URI syntax. The example didn't seem to apply to my issue when I first reviewed it since I wasn't trying to specify column types.

Ok, in that case I'll chicken out and not test the url. But as you suggested, provide a better example of the url.

I updated the documentation of each function that uses the parameter. I also added this entry to the troubleshooting guide.

1. Is the URL/URI correct? Notice the url typically resembles https://bbmc.ouhsc.edu/redcap/api/ and not https://bbmc.ouhsc.edu/ (even if https://bbmc.ouhsc.edu/ redirects to https://bbmc.ouhsc.edu/redcap).