The validating yaml parameter plugin contributes a new parameter type to Jenkins that allows Yaml validation of the entered contents.

This parameter plugin is used in the job configuration page by enabling parameterized builds.

You just need to configure the parameter by entering a name, default value (yaml), failed validation message and the parameter description:

When a build is requested, the user is prompted with the parameters to enter. If the user types bad yaml contents, then there's a validation error return after the form is submitted.