diff --git a/packit_service/worker/checker/abstract.py b/packit_service/worker/checker/abstract.py
index ac7b180a1..542595af6 100644
--- a/packit_service/worker/checker/abstract.py
+++ b/packit_service/worker/checker/abstract.py
@@ -18,6 +18,9 @@
 
 
 class Checker(ConfigFromEventMixin, PackitAPIWithDownstreamMixin):
+    """Verifies conditions before proceeding based on supplied event data,
+    task name, job and package configuration."""
+
     def __init__(
         self,
         package_config: PackageConfig,
diff --git a/packit_service/worker/checker/bodhi.py b/packit_service/worker/checker/bodhi.py
index 57a817e25..22bd0c3cb 100644
--- a/packit_service/worker/checker/bodhi.py
+++ b/packit_service/worker/checker/bodhi.py
@@ -176,6 +176,8 @@ def _pre_check(self) -> bool:
 
 
 class IsAuthorAPackager(ActorChecker, PackitAPIWithDownstreamMixin):
+    """Verifies that the author is a packager if the event is `pagure.pr.Comment`."""
+
     def _pre_check(self) -> bool:
         if self.data.event_type not in (pagure.pr.Comment.event_type(),) or self.is_packager(
             user=self.actor
diff --git a/packit_service/worker/checker/copr.py b/packit_service/worker/checker/copr.py
index 57e36088b..17429ee71 100644
--- a/packit_service/worker/checker/copr.py
+++ b/packit_service/worker/checker/copr.py
@@ -36,6 +36,9 @@ class IsGitForgeProjectAndEventOk(
     ConfigFromEventMixin,
     GetCoprBuildJobHelperMixin,
 ):
+    """Verifies that mergerequest isn't closed, is in appropriate stage
+    and in case of custom projects that it satisfies criteria for using Copr."""
+
     def pre_check(
         self,
     ) -> bool:
diff --git a/packit_service/worker/checker/distgit.py b/packit_service/worker/checker/distgit.py
index dc877ab8d..d911dadf7 100644
--- a/packit_service/worker/checker/distgit.py
+++ b/packit_service/worker/checker/distgit.py
@@ -30,6 +30,11 @@
 
 
 class LabelsOnDistgitPR(Checker, GetPagurePullRequestMixin):
+    """Verifies that state of labels on the PR matches the configuration.
+
+    The check passes also if the event is not a `pagure.push.Commit`,
+    or if no configuration exists."""
+
     def pre_check(self) -> bool:
         if self.data.event_type not in (pagure.push.Commit.event_type(),) or not (
             self.job_config.require.label.present or self.job_config.require.label.absent
@@ -44,6 +49,11 @@ def pre_check(self) -> bool:
 
 
 class PermissionOnDistgit(Checker, GetPagurePullRequestMixin):
+    """Verifies that author of given event has permissions for the workflow.
+
+    If the check fails for `pagure.pr.Comment` event, a notification is posted
+    in the same thread."""
+
     def pre_check(self) -> bool:
         if self.data.event_type in (
             pagure.push.Commit.event_type(),
@@ -129,6 +139,8 @@ def pre_check(self) -> bool:
 
 
 class PermissionOnDistgitForFedoraCI(Checker, GetPagurePullRequestMixin):
+    """Verifies if user posting a comment with command is a packager."""
+
     def pre_check(self) -> bool:
         if self.data.event_type in (pagure.pr.Comment.event_type(),):
             comment = self.data.event_dict.get("comment", "")
@@ -275,6 +287,13 @@ def pre_check(self) -> bool:
 
 
 class IsUpstreamTagMatchingConfig(Checker):
+    """Verifies that the tag is either among configured included tags,
+    or not among configured excluded tags.
+
+    If the tag in event is `None`, for example in case of pull-from-upstream
+    retriggering the check passes.
+    """
+
     def pre_check(self) -> bool:
         tag = self.data.tag_name
 
diff --git a/packit_service/worker/checker/open_scan_hub.py b/packit_service/worker/checker/open_scan_hub.py
index 72f4440af..5f4d60b97 100644
--- a/packit_service/worker/checker/open_scan_hub.py
+++ b/packit_service/worker/checker/open_scan_hub.py
@@ -15,6 +15,8 @@
 class RawhideX86Target(
     Checker,
 ):
+    """Verifies that build targets include `fedora-rawhide-x86_64`."""
+
     def pre_check(self) -> bool:
         branches = aliases.get_build_targets(
             *self.job_config.targets,
diff --git a/packit_service/worker/checker/run_condition.py b/packit_service/worker/checker/run_condition.py
index 2a8ca74d6..1a108d771 100644
--- a/packit_service/worker/checker/run_condition.py
+++ b/packit_service/worker/checker/run_condition.py
@@ -34,6 +34,9 @@
 
 
 class IsRunConditionSatisfied(Checker, ConfigFromEventMixin, PackitAPIWithUpstreamMixin):
+    """Verifies if the user defined run_condition action passes,
+    optionally cloning the repository to evaluate the condition in the project's context."""
+
     def __init__(
         self,
         package_config: PackageConfig,
diff --git a/packit_service/worker/checker/vm_image.py b/packit_service/worker/checker/vm_image.py
index 27717132a..e2dc3c4d1 100644
--- a/packit_service/worker/checker/vm_image.py
+++ b/packit_service/worker/checker/vm_image.py
@@ -72,6 +72,8 @@ def report_status(self, status: VMImageBuildStatus, markdown_content: str):
 
 
 class IsCoprBuildForChrootOk(Checker, GetVMImageBuildReporterFromJobHelperMixin):
+    """Verifies that copr build is associated with given task."""
+
     def pre_check(
         self,
     ) -> bool:
diff --git a/packit_service/worker/handlers/abstract.py b/packit_service/worker/handlers/abstract.py
index 3fbba6abb..99869651f 100644
--- a/packit_service/worker/handlers/abstract.py
+++ b/packit_service/worker/handlers/abstract.py
@@ -328,6 +328,8 @@ def _clean_workplace(self):
 
     @staticmethod
     def get_checkers() -> tuple[type[Checker], ...]:
+        """Return tuple of Checker objects to be one by one executed
+        during pre_check."""
         return ()
 
     @classmethod
@@ -338,6 +340,9 @@ def pre_check(
         event: dict,
     ) -> bool:
         """
+        Verify that the handler should be used for incoming event with given
+        job and package configuration.
+
         Returns
             bool: False if we have to skip the job execution.
         """