We are fairly limited in the data that we can pass to a workflow when triggering via the API because pipeline parameters have to be declared in config.yml using primitive types. This make is difficult to send an object to be decoded in a library during one of the steps.

For instance, we currently have to send a comma-delimited string for one of our parameters. We're also exploring the need to send an entire object from a local "build creator" app to the workflow as an existing string will no longer suffice.

Being able to pass a JSON payload that could be accessed in an environment variable rather than rendered in the config.yml file would be a huge improvement and would bring this on par with GitHub Action event triggers.