fzzf: In addition to the documentation carloss provided, here are some example pipeline configurations [1][2]. Note that you need to provide pipeline.success and/or pipeline.failure, so that Zuul knows what to do, i.e. where to report, when a dequeued item succeeds or fails (relevant documentation here [3]). Something else interesting to note is that a pipeline.success/pipeline.failure key can have an empty dictionary as a value, so that it won't set any Gerrit labels [4], but only comment the job results.

[1] https://opendev.org/openstack/project-config/src/branch/master/zuul.d/pipelines.yaml#L45-L57
[2] https://opendev.org/openstack/project-config/src/branch/master/zuul.d/pipelines.yaml#L133-L136
[3] https://zuul-ci.org/docs/zuul/latest/config/pipeline.html#attr-pipeline.success
[4] https://gerrit-documentation.storage.googleapis.com/Documentation/3.5.1/config-labels.html