diff --git a/petab_select/__init__.py b/petab_select/__init__.py
index bd2994f5..b2455da3 100644
--- a/petab_select/__init__.py
+++ b/petab_select/__init__.py
@@ -1,5 +1,7 @@
 """Model selection extension for PEtab."""
 
+import sys
+
 from .candidate_space import *
 from .constants import *
 from .criteria import *
@@ -9,3 +11,9 @@
 from .model_subspace import *
 from .problem import *
 from .ui import *
+
+__all__ = [
+    x
+    for x in dir(sys.modules[__name__])
+    if not x.startswith('_') and x != 'sys'
+]
diff --git a/petab_select/candidate_space.py b/petab_select/candidate_space.py
index 8aaa9e04..1154ffa4 100644
--- a/petab_select/candidate_space.py
+++ b/petab_select/candidate_space.py
@@ -28,6 +28,17 @@
 from .handlers import TYPE_LIMIT, LimitHandler
 from .model import Model, default_compare
 
+__all__ = [
+    'BackwardCandidateSpace',
+    'BidirectionalCandidateSpace',
+    'BruteForceCandidateSpace',
+    'CandidateSpace',
+    'FamosCandidateSpace',
+    'ForwardAndBackwardCandidateSpace',
+    'ForwardCandidateSpace',
+    'LateralCandidateSpace',
+]
+
 
 class CandidateSpace(abc.ABC):
     """A base class for collecting candidate models.
diff --git a/petab_select/constants.py b/petab_select/constants.py
index 0a7bee3e..d5e566a2 100644
--- a/petab_select/constants.py
+++ b/petab_select/constants.py
@@ -1,4 +1,5 @@
 """Constants for the PEtab Select package."""
+import sys
 from enum import Enum
 from pathlib import Path
 from typing import Dict, List, Literal, Union
@@ -164,3 +165,12 @@ class Criterion(str, Enum):
     Method.FORWARD,
     Method.FORWARD_AND_BACKWARD,
 ]
+
+
+__all__ = [
+    x
+    for x in dir(sys.modules[__name__])
+    if not x.startswith('_')
+    and x not in ('sys', "Enum", "Path", "Dict", "List", "Literal", "Union")
+]
+print(__all__)
diff --git a/petab_select/criteria.py b/petab_select/criteria.py
index 6e6db4b0..8bb8c283 100644
--- a/petab_select/criteria.py
+++ b/petab_select/criteria.py
@@ -9,7 +9,12 @@
 
 from .constants import PETAB_PROBLEM, Criterion  # LH,; LLH,; NLLH,
 
-# from .model import Model
+__all__ = [
+    'calculate_aic',
+    'calculate_aicc',
+    'calculate_bic',
+    'CriterionComputer',
+]
 
 
 # use as attribute e.g. `Model.criterion_computer`?
diff --git a/petab_select/misc.py b/petab_select/misc.py
index d690fae3..48cbc864 100644
--- a/petab_select/misc.py
+++ b/petab_select/misc.py
@@ -9,6 +9,16 @@
     TYPE_PARAMETER_OPTIONS,
 )
 
+__all__ = [
+    'hashify',
+    'hash_parameter_dict',
+    'hash_parameter_options',
+    'hash_str',
+    'hash_list',
+    'snake_case_to_camel_case',
+    'parameter_string_to_value',
+]
+
 
 def hashify(x: Any) -> str:
     """Generate a hash.
diff --git a/petab_select/model.py b/petab_select/model.py
index e3dd4792..64812e1a 100644
--- a/petab_select/model.py
+++ b/petab_select/model.py
@@ -36,6 +36,13 @@
 )
 from .petab import PetabMixin
 
+__all__ = [
+    'Model',
+    'default_compare',
+    'models_from_yaml_list',
+    'models_to_yaml_list',
+]
+
 
 class Model(PetabMixin):
     """A (possibly uncalibrated) model.
diff --git a/petab_select/model_space.py b/petab_select/model_space.py
index b545a653..6ce146fd 100644
--- a/petab_select/model_space.py
+++ b/petab_select/model_space.py
@@ -21,6 +21,13 @@
 from .model import Model
 from .model_subspace import ModelSubspace
 
+__all__ = [
+    "ModelSpace",
+    "get_model_space_df",
+    "read_model_space_file",
+    "write_model_space_df",
+]
+
 
 def read_model_space_file(filename: str) -> TextIO:
     """Read a model space file.
diff --git a/petab_select/model_subspace.py b/petab_select/model_subspace.py
index 9b40f696..f407d3a7 100644
--- a/petab_select/model_subspace.py
+++ b/petab_select/model_subspace.py
@@ -26,6 +26,10 @@
 from .model import Model
 from .petab import PetabMixin
 
+__all__ = [
+    'ModelSubspace',
+]
+
 
 class ModelSubspace(PetabMixin):
     """Efficient representation of exponentially large model subspaces.
diff --git a/petab_select/petab.py b/petab_select/petab.py
index e1aa697c..b676e56f 100644
--- a/petab_select/petab.py
+++ b/petab_select/petab.py
@@ -7,6 +7,10 @@
 
 from .constants import PETAB_ESTIMATE_FALSE, TYPE_PARAMETER_DICT, TYPE_PATH
 
+__all__ = [
+    'PetabMixin',
+]
+
 
 class PetabMixin:
     """Useful things for classes that contain a PEtab problem.
diff --git a/petab_select/problem.py b/petab_select/problem.py
index 0e5cbebe..a8f068c0 100644
--- a/petab_select/problem.py
+++ b/petab_select/problem.py
@@ -20,6 +20,10 @@
 from .model import Model, default_compare
 from .model_space import ModelSpace
 
+__all__ = [
+    'Problem',
+]
+
 
 class Problem(abc.ABC):
     """Handle everything related to the model selection problem.
diff --git a/petab_select/ui.py b/petab_select/ui.py
index bdb34b82..89a0e10b 100644
--- a/petab_select/ui.py
+++ b/petab_select/ui.py
@@ -9,6 +9,14 @@
 from .model import Model, default_compare
 from .problem import Problem
 
+__all__ = [
+    'candidates',
+    'model_to_petab',
+    'models_to_petab',
+    'best',
+    'write_summary_tsv',
+]
+
 
 def candidates(
     problem: Problem,