--- a/taskcluster/taskgraph/transforms/signing.py
+++ b/taskcluster/taskgraph/transforms/signing.py
@@ -58,18 +58,18 @@ signing_description_schema = Schema({
     # unique label to describe this signing task, defaults to {dep.label}-signing
     Optional('label'): basestring,
 
     # treeherder is allowed here to override any defaults we use for signing.  See
     # taskcluster/taskgraph/transforms/task.py for the schema details, and the
     # below transforms for defaults of various values.
     Optional('treeherder'): task_description_schema['treeherder'],
 
-    # If True, announce to a specific route when done, so that funsize
-    # can start its partial mar generation. For nightly builds only.
+    # If True, adds a route which funsize uses to schedule generation of partial mar
+    # files for updates. Expected to be added on nightly builds only.
     Optional('use_funsize_route'): bool,
 })
 
 
 @transforms.add
 def validate(config, jobs):
     for job in jobs:
         label = job.get('dependent-task', object).__dict__.get('label', '?no-label?')
@@ -117,11 +117,12 @@ def make_task_description(config, jobs):
             'scopes': ["project:releng:signing:cert:nightly-signing"] + signing_format_scopes,
             'dependencies': {job['depname']: dep_job.label},
             'attributes': attributes,
             'run-on-projects': dep_job.attributes.get('run_on_projects'),
             'treeherder': treeherder,
         }
 
         if job.get('use_funsize_route', False):
-            task['routes'] = ["project.releng.funsize.{project}.level-3".format(project=config.params['project'])]
+            task['routes'] = ["project.releng.funsize.{project}.level-{level}".format(
+                project=config.params['project'], level=config.params['level'])]
 
         yield task