diff --git a/src/tof/__init__.py b/src/tof/__init__.py
index d621bed..8ca42eb 100644
--- a/src/tof/__init__.py
+++ b/src/tof/__init__.py
@@ -1,11 +1,27 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright (c) 2023 Scipp contributors (https://github.com/scipp)
 
-# flake8: noqa F401
-
 from .chopper import AntiClockwise, Chopper, ChopperReading, Clockwise
 from .detector import Detector, DetectorReading
+from .facilities import library as facilities
 from .model import Model
 from .reading import ComponentReading, ReadingData, ReadingField
 from .result import Result
 from .source import Source, SourceParameters
+
+__all__ = [
+    'AntiClockwise',
+    'Chopper',
+    'ChopperReading',
+    'Clockwise',
+    'ComponentReading',
+    'Detector',
+    'DetectorReading',
+    'facilities',
+    'Model',
+    'ReadingData',
+    'ReadingField',
+    'Result',
+    'Source',
+    'SourceParameters',
+]
diff --git a/src/tof/facilities/__init__.py b/src/tof/facilities/__init__.py
index b53d376..0d9e839 100644
--- a/src/tof/facilities/__init__.py
+++ b/src/tof/facilities/__init__.py
@@ -1,6 +1,8 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright (c) 2023 Scipp contributors (https://github.com/scipp)
 
-# flake8: noqa F401
+from .ess_pulse import pulse as esspulse
 
-from .ess_pulse import pulse as ess
+library = {'ess': esspulse}
+
+__all__ = ['library']
diff --git a/src/tof/facilities/ess_pulse.py b/src/tof/facilities/ess_pulse.py
index ec62796..4c81853 100644
--- a/src/tof/facilities/ess_pulse.py
+++ b/src/tof/facilities/ess_pulse.py
@@ -1,6 +1,11 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright (c) 2023 Scipp contributors (https://github.com/scipp)
 
+"""
+The data here was obtained from the McStas model of the ESS moderator.
+See https://www2.mcstas.org/download/components/3.4_current/sources/ESS_butterfly.html.
+"""
+
 import scipp as sc
 
 from ..utils import FacilityPulse
diff --git a/src/tof/source.py b/src/tof/source.py
index 9b2b603..b64e6bd 100644
--- a/src/tof/source.py
+++ b/src/tof/source.py
@@ -10,7 +10,7 @@
 import scipp as sc
 from scipp.scipy.interpolate import interp1d
 
-from . import facilities
+from .facilities import library as facilities
 from .utils import Plot, wavelength_to_speed
 
 TIME_UNIT = "us"
@@ -208,7 +208,7 @@ def __init__(
         self.data = None
 
         if facility is not None:
-            facility_params = getattr(facilities, self.facility)
+            facility_params = facilities[self.facility]
             self.frequency = facility_params.frequency
             pulse_params = _make_pulses(
                 neutrons=self.neutrons,