diff --git a/.github/ISSUE_TEMPLATE/bug_report.md b/.github/ISSUE_TEMPLATE/bug_report.md
index d482e09..b89206c 100644
--- a/.github/ISSUE_TEMPLATE/bug_report.md
+++ b/.github/ISSUE_TEMPLATE/bug_report.md
@@ -1,24 +1,21 @@
----
+______________________________________________________________________
 
-name: Bug Report
-about: Create a bug report to help us improve pytask-stata
-title: "BUG:"
-labels: "bug"
+name: Bug Report about: Create a bug report to help us improve pytask-stata title:
+"BUG:" labels: "bug"
 
----
+______________________________________________________________________
 
 - [ ] I have checked that this issue has not already been reported.
 
 - [ ] I have confirmed this bug exists on the latest version of pytask-stata.
 
-- [ ] (optional) I have confirmed this bug exists on the `main` branch of
-  pytask-stata.
+- [ ] (optional) I have confirmed this bug exists on the `main` branch of pytask-stata.
 
----
+______________________________________________________________________
 
-**Note**: Please read [this
-guide](https://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports) detailing
-how to provide the necessary information for us to reproduce your bug.
+**Note**: Please read
+[this guide](https://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports)
+detailing how to provide the necessary information for us to reproduce your bug.
 
 #### Code Sample, a copy-pastable example
 
diff --git a/.github/ISSUE_TEMPLATE/documentation.md b/.github/ISSUE_TEMPLATE/documentation.md
index 90389c7..eba1e97 100644
--- a/.github/ISSUE_TEMPLATE/documentation.md
+++ b/.github/ISSUE_TEMPLATE/documentation.md
@@ -1,11 +1,9 @@
----
+______________________________________________________________________
 
-name: Documentation Improvement
-about: Report wrong or missing documentation
-title: "DOC:"
-labels: "documentation"
+name: Documentation Improvement about: Report wrong or missing documentation title:
+"DOC:" labels: "documentation"
 
----
+______________________________________________________________________
 
 #### Location of the documentation
 
diff --git a/.github/ISSUE_TEMPLATE/enhancement.md b/.github/ISSUE_TEMPLATE/enhancement.md
index 5296f8d..5402874 100644
--- a/.github/ISSUE_TEMPLATE/enhancement.md
+++ b/.github/ISSUE_TEMPLATE/enhancement.md
@@ -1,16 +1,14 @@
----
+______________________________________________________________________
 
-name: Enhancement
-about: Suggest an idea for pytask-stata
-title: "ENH:"
-labels: "enhancement"
+name: Enhancement about: Suggest an idea for pytask-stata title: "ENH:" labels:
+"enhancement"
 
----
+______________________________________________________________________
 
 #### Is your feature request related to a problem?
 
-Provide a description of what the problem is, e.g. "I wish I could use pytask-stata
-to do [...]".
+Provide a description of what the problem is, e.g. "I wish I could use pytask-stata to
+do \[...\]".
 
 #### Describe the solution you'd like
 
diff --git a/.github/ISSUE_TEMPLATE/question.md b/.github/ISSUE_TEMPLATE/question.md
index 46dfc30..bad0800 100644
--- a/.github/ISSUE_TEMPLATE/question.md
+++ b/.github/ISSUE_TEMPLATE/question.md
@@ -1,17 +1,15 @@
----
+______________________________________________________________________
 
-name: Submit Question
-about: Ask a general question about pytask-stata
-title: "QST:"
+name: Submit Question about: Ask a general question about pytask-stata title: "QST:"
 labels: "question"
 
----
+______________________________________________________________________
 
 #### Question about pytask-stata
 
-**Note**: If you'd still like to submit a question, please read [this guide](
-https://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports) detailing how to
-provide the necessary information for us to reproduce your question.
+**Note**: If you'd still like to submit a question, please read
+[this guide](https://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports)
+detailing how to provide the necessary information for us to reproduce your question.
 
 ```python
 # Your code here, if applicable
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index c3d6d49..aea16c5 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -68,10 +68,34 @@ repos:
     hooks:
     -   id: interrogate
         args: [-v, --fail-under=40, src, tests]
+-   repo: https://github.com/executablebooks/mdformat
+    rev: 0.7.14
+    hooks:
+    -   id: mdformat
+        additional_dependencies: [
+            mdformat-gfm,
+            mdformat-black,
+        ]
+        args: [--wrap, "88"]
 - repo: https://github.com/codespell-project/codespell
   rev: v2.1.0
   hooks:
     -   id: codespell
+-   repo: https://github.com/pre-commit/mirrors-mypy
+    rev: 'v0.931'
+    hooks:
+    -   id: mypy
+        args: [
+            --no-strict-optional,
+            --ignore-missing-imports,
+        ]
+        additional_dependencies: [
+            attrs,
+            click,
+            types-setuptools
+        ]
+        pass_filenames: false
+        language_version: "3.9"
 -   repo: https://github.com/mgedmin/check-manifest
     rev: "0.48"
     hooks:
diff --git a/CHANGES.md b/CHANGES.md
index cb54a22..016fbe0 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,58 +1,51 @@
 # Changes
 
-This is a record of all past pytask-stata releases and what went into
-them in reverse chronological order. Releases follow [semantic
-versioning](https://semver.org/) and all releases are available on
-[PyPI](https://pypi.org/project/pytask-stata) and
+This is a record of all past pytask-stata releases and what went into them in reverse
+chronological order. Releases follow [semantic versioning](https://semver.org/) and all
+releases are available on [PyPI](https://pypi.org/project/pytask-stata) and
 [Anaconda.org](https://anaconda.org/conda-forge/pytask-stata).
 
 ## 0.2.0 - 2022-xx-xx
 
--   {pull}`20` removes an unnecessary hook implementation.
+- {pull}`18` adds typing to the package.
+- {pull}`20` removes an unnecessary hook implementation.
 
 ## 0.1.2 - 2022-02-08
 
--   {pull}`19` fixes the minimum python and
-    pytask version.
+- {pull}`19` fixes the minimum python and pytask version.
 
 ## 0.1.1 - 2022-02-07
 
--   {pull}`16` skips concurrent CI builds.
--   {pull}`17` deprecates Python 3.6 and adds
-    support for Python 3.10.
+- {pull}`16` skips concurrent CI builds.
+- {pull}`17` deprecates Python 3.6 and adds support for Python 3.10.
 
 ## 0.1.0 - 2021-07-21
 
--   {pull}`11` fixes the `README.rst`.
--   {pull}`13` replaces versioneer with
-    setuptools-scm.
--   {pull}`14` fixes tests and aligns
-    pytask-stata with pytask v0.1.0.
+- {pull}`11` fixes the `README.rst`.
+- {pull}`13` replaces versioneer with setuptools-scm.
+- {pull}`14` fixes tests and aligns pytask-stata with pytask v0.1.0.
 
 ## 0.0.6 - 2021-03-05
 
--   {pull}`10` fixes the version of the package.
+- {pull}`10` fixes the version of the package.
 
 ## 0.0.5 - 2021-03-04
 
--   {pull}`7` fix some post-release issues.
--   {pull}`9` adds dependencies to `setup.py`.
+- {pull}`7` fix some post-release issues.
+- {pull}`9` adds dependencies to `setup.py`.
 
 ## 0.0.4 - 2021-02-25
 
--   {pull}`6` prepares pytask-stata to be
-    published on PyPI, adds versioneer and more.
+- {pull}`6` prepares pytask-stata to be published on PyPI, adds versioneer and more.
 
 ## 0.0.3 - 2021-01-16
 
--   {pull}`4` removes log file handling on UNIX
-    and raises an error if run in parallel.
+- {pull}`4` removes log file handling on UNIX and raises an error if run in parallel.
 
 ## 0.0.2 - 2020-10-30
 
--   {pull}`1` makes pytask-stata work with pytask
-    v0.0.9.
+- {pull}`1` makes pytask-stata work with pytask v0.0.9.
 
 ## 0.0.1 - 2020-10-04
 
--   Release v0.0.1.
+- Release v0.0.1.
diff --git a/README.md b/README.md
index affe05d..c7a558a 100644
--- a/README.md
+++ b/README.md
@@ -10,18 +10,16 @@
 [![pre-commit.ci status](https://results.pre-commit.ci/badge/github/pytask-dev/pytask-stata/main.svg)](https://results.pre-commit.ci/latest/github/pytask-dev/pytask-stata/main)
 [![image](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)
 
-------------------------------------------------------------------------
+______________________________________________________________________
 
-Run Stata\'s do-files with pytask.
+Run Stata's do-files with pytask.
 
 ## Installation
 
-pytask-stata is available on
-[PyPI](https://pypi.org/project/pytask-stata) and
-[Anaconda.org](https://anaconda.org/conda-forge/pytask-stata). Install
-it with
+pytask-stata is available on [PyPI](https://pypi.org/project/pytask-stata) and
+[Anaconda.org](https://anaconda.org/conda-forge/pytask-stata). Install it with
 
-``` console
+```console
 $ pip install pytask-stata
 
 # or
@@ -29,20 +27,20 @@ $ pip install pytask-stata
 $ conda install -c conda-forge pytask-stata
 ```
 
-You also need to have Stata installed on your system and have the
-executable on your system\'s PATH. If you do not know how to do it,
-[here](https://superuser.com/a/284351) is an explanation.
+You also need to have Stata installed on your system and have the executable on your
+system's PATH. If you do not know how to do it, [here](https://superuser.com/a/284351)
+is an explanation.
 
 ## Usage
 
-Similarly to normal task functions which execute Python code, you define
-tasks to execute scripts written in Stata with Python functions. The
-difference is that the function body does not contain any logic, but the
-decorator tells pytask how to handle the task.
+Similarly to normal task functions which execute Python code, you define tasks to
+execute scripts written in Stata with Python functions. The difference is that the
+function body does not contain any logic, but the decorator tells pytask how to handle
+the task.
 
 Here is an example where you want to run `script.do`.
 
-``` python
+```python
 import pytask
 
 
@@ -52,24 +50,23 @@ def task_run_do_file():
     pass
 ```
 
-When executing a do-file, the current working directory changes to the
-directory where the script is located. This allows you, for example, to
-reference every data set you want to read with a relative path from the
-script.
+When executing a do-file, the current working directory changes to the directory where
+the script is located. This allows you, for example, to reference every data set you
+want to read with a relative path from the script.
 
 ### Dependencies and Products
 
-Dependencies and products can be added as with a normal pytask task
-using the `@pytask.mark.depends_on` and `@pytask.mark.produces`
-decorators. which is explained in this
+Dependencies and products can be added as with a normal pytask task using the
+`@pytask.mark.depends_on` and `@pytask.mark.produces` decorators. which is explained in
+this
 [tutorial](https://pytask-dev.readthedocs.io/en/stable/tutorials/defining_dependencies_products.html).
 
 ### Accessing dependencies and products in the script
 
-The decorator can be used to pass command line arguments to your Stata
-executable. For example, pass the path of the product with
+The decorator can be used to pass command line arguments to your Stata executable. For
+example, pass the path of the product with
 
-``` python
+```python
 @pytask.mark.stata(script="script.do", options="auto.dta")
 @pytask.mark.produces("auto.dta")
 def task_run_do_file():
@@ -78,7 +75,7 @@ def task_run_do_file():
 
 And in your `script.do`, you can intercept the value with
 
-``` do
+```do
 * Intercept command line argument and save to macro named 'produces'.
 args produces
 
@@ -86,14 +83,13 @@ sysuse auto, clear
 save "`produces'"
 ```
 
-The relative path inside the do-file works only because the pytask-stata
-switches the current working directory to the directory of the do-file
-before the task is executed.
+The relative path inside the do-file works only because the pytask-stata switches the
+current working directory to the directory of the do-file before the task is executed.
 
-To make the task independent from the current working directory, pass
-the full path as an command line argument. Here is an example.
+To make the task independent from the current working directory, pass the full path as
+an command line argument. Here is an example.
 
-``` python
+```python
 # Absolute path to the build directory.
 from src.config import BLD
 
@@ -106,14 +102,12 @@ def task_run_do_file():
 
 ### Repeating tasks with different scripts or inputs
 
-You can also parametrize the execution of scripts, meaning executing
-multiple do-files as well as passing different command line arguments to
-the same do-file.
+You can also parametrize the execution of scripts, meaning executing multiple do-files
+as well as passing different command line arguments to the same do-file.
 
-The following task executes two do-files which produce different
-outputs.
+The following task executes two do-files which produce different outputs.
 
-``` python
+```python
 for i in range(2):
 
     @pytask.mark.task
@@ -129,25 +123,22 @@ pytask-stata can be configured with the following options.
 
 *`stata_keep_log`*
 
-Use this option to keep the `.log` files which are produced for
-every task. This option is useful to debug Stata tasks. Set the
-option via the configuration file with
+Use this option to keep the `.log` files which are produced for every task. This option
+is useful to debug Stata tasks. Set the option via the configuration file with
 
 ```toml
 [tool.pytask.ini_options]
 stata_keep_log = true
 ```
 
-The option is also available in the command line interface via the
-`--stata-keep-log` flag.
-
+The option is also available in the command line interface via the `--stata-keep-log`
+flag.
 
 *`stata_check_log_lines`*
 
-Use this option to vary the number of lines in the log file which
-are checked for error codes. It also controls the number of lines
-displayed on errors. Use any integer greater than zero. Here is the
-entry in the configuration file
+Use this option to vary the number of lines in the log file which are checked for error
+codes. It also controls the number of lines displayed on errors. Use any integer greater
+than zero. Here is the entry in the configuration file
 
 ```toml
 [tool.pytask.ini_options]
@@ -156,7 +147,7 @@ stata_check_log_lines = 10
 
 and here via the command line interface
 
-``` console
+```console
 $ pytask build --stata-check-log-lines 10
 ```
 
diff --git a/pyproject.toml b/pyproject.toml
index 692c35b..35ff30f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -5,3 +5,20 @@ build-backend = "setuptools.build_meta"
 
 [tool.setuptools_scm]
 write_to = "src/pytask_stata/_version.py"
+
+
+[tool.mypy]
+files = ["src", "tests"]
+check_untyped_defs = true
+disallow_any_generics = true
+disallow_incomplete_defs = true
+disallow_untyped_defs = true
+no_implicit_optional = true
+warn_redundant_casts = true
+warn_unused_ignores = true
+
+
+[[tool.mypy.overrides]]
+module = "tests.*"
+disallow_untyped_defs = false
+ignore_errors = true
diff --git a/src/pytask_stata/collect.py b/src/pytask_stata/collect.py
index fa535da..6853faf 100644
--- a/src/pytask_stata/collect.py
+++ b/src/pytask_stata/collect.py
@@ -5,6 +5,7 @@
 import subprocess
 from pathlib import Path
 from types import FunctionType
+from typing import Any
 
 from pytask import depends_on
 from pytask import has_mark
@@ -13,6 +14,7 @@
 from pytask import parse_nodes
 from pytask import produces
 from pytask import remove_marks
+from pytask import Session
 from pytask import Task
 from pytask_stata.shared import convert_task_id_to_name_of_log_file
 from pytask_stata.shared import stata
@@ -28,7 +30,9 @@ def run_stata_script(
 
 
 @hookimpl
-def pytask_collect_task(session, path, name, obj):
+def pytask_collect_task(
+    session: Session, path: Path, name: str, obj: Any
+) -> Task | None:
     """Perform some checks and prepare the task function."""
     __tracebackhide__ = True
 
@@ -59,7 +63,7 @@ def pytask_collect_task(session, path, name, obj):
         task = Task(
             base_name=name,
             path=path,
-            function=_copy_func(run_stata_script),
+            function=_copy_func(run_stata_script),  # type: ignore
             depends_on=dependencies,
             produces=products,
             markers=markers,
@@ -93,14 +97,16 @@ def pytask_collect_task(session, path, name, obj):
         task.function = stata_function
 
         return task
+    else:
+        return None
 
 
-def _parse_stata_mark(mark):
+def _parse_stata_mark(mark: Mark) -> Mark:
     """Parse a Julia mark."""
     script, options = stata(**mark.kwargs)
 
     parsed_kwargs = {}
-    for arg_name, value, default in [
+    for arg_name, value, default in [  # type: ignore
         ("script", script, None),
         ("options", options, []),
     ]:
diff --git a/src/pytask_stata/config.py b/src/pytask_stata/config.py
index a37ed2d..b779250 100644
--- a/src/pytask_stata/config.py
+++ b/src/pytask_stata/config.py
@@ -11,7 +11,11 @@
 
 
 @hookimpl
-def pytask_parse_config(config, config_from_cli, config_from_file):
+def pytask_parse_config(
+    config: dict[str, Any],
+    config_from_cli: dict[str, Any],
+    config_from_file: dict[str, Any],
+) -> None:
     """Register the r marker."""
     config["markers"]["stata"] = "Tasks which are executed with Stata."
     config["platform"] = sys.platform
@@ -41,7 +45,7 @@ def pytask_parse_config(config, config_from_cli, config_from_file):
     )
 
 
-def _nonnegative_nonzero_integer(x):
+def _nonnegative_nonzero_integer(x: Any) -> int:
     """Check for nonnegative and nonzero integer."""
     if x is not None:
         try:
diff --git a/src/pytask_stata/execute.py b/src/pytask_stata/execute.py
index 1879bda..db12876 100644
--- a/src/pytask_stata/execute.py
+++ b/src/pytask_stata/execute.py
@@ -5,12 +5,14 @@
 
 from pytask import has_mark
 from pytask import hookimpl
+from pytask import Session
+from pytask import Task
 from pytask_stata.shared import convert_task_id_to_name_of_log_file
 from pytask_stata.shared import STATA_COMMANDS
 
 
 @hookimpl
-def pytask_execute_task_setup(session, task):
+def pytask_execute_task_setup(session: Session, task: Task) -> None:
     """Check if Stata is found on the PATH."""
     if has_mark(task, "stata") and session.config["stata"] is None:
         raise RuntimeError(
@@ -22,7 +24,7 @@ def pytask_execute_task_setup(session, task):
 
 
 @hookimpl
-def pytask_execute_task_teardown(session, task):
+def pytask_execute_task_teardown(session: Session, task: Task) -> None:
     """Check if the log file contains no error code.
 
     Stata has the weird behavior of always returning an exit code of 0 even if an error
diff --git a/src/pytask_stata/parametrize.py b/src/pytask_stata/parametrize.py
index 300ee31..d2f49bf 100644
--- a/src/pytask_stata/parametrize.py
+++ b/src/pytask_stata/parametrize.py
@@ -1,12 +1,15 @@
 """Parametrize tasks."""
 from __future__ import annotations
 
+from typing import Any
+from typing import Callable
+
 import pytask
-from pytask import hookimpl
+from _pytask.config import hookimpl
 
 
 @hookimpl
-def pytask_parametrize_kwarg_to_marker(obj, kwargs):
+def pytask_parametrize_kwarg_to_marker(obj: Callable[..., Any], kwargs: Any) -> None:
     """Attach parametrized stata arguments to the function with a marker."""
     if callable(obj):
         if "stata" in kwargs:
diff --git a/src/pytask_stata/plugin.py b/src/pytask_stata/plugin.py
index b57f5db..7efaaf1 100644
--- a/src/pytask_stata/plugin.py
+++ b/src/pytask_stata/plugin.py
@@ -1,7 +1,8 @@
 """Register hook specifications and implementations."""
 from __future__ import annotations
 
-from pytask import hookimpl
+from _pytask.config import hookimpl
+from pluggy import PluginManager
 from pytask_stata import cli
 from pytask_stata import collect
 from pytask_stata import config
@@ -10,7 +11,7 @@
 
 
 @hookimpl
-def pytask_add_hooks(pm):
+def pytask_add_hooks(pm: PluginManager) -> None:
     """Register hook implementations."""
     pm.register(cli)
     pm.register(collect)
diff --git a/src/pytask_stata/shared.py b/src/pytask_stata/shared.py
index a188e18..e9f985a 100644
--- a/src/pytask_stata/shared.py
+++ b/src/pytask_stata/shared.py
@@ -3,6 +3,7 @@
 
 import sys
 from pathlib import Path
+from typing import Any
 from typing import Iterable
 from typing import Sequence
 
@@ -71,7 +72,7 @@ def task_r():
 
 
 def stata(
-    *args,
+    *args: Any,
     script: str | Path | None = None,
     options: str | Iterable[str] | None = None,
 ) -> tuple[str | Path | None, str | Iterable[str] | None]:
@@ -90,7 +91,7 @@ def stata(
     return script, options
 
 
-def convert_task_id_to_name_of_log_file(id_):
+def convert_task_id_to_name_of_log_file(id_: str) -> str:
     """Convert task to id to name of log file.
 
     If one passes the complete task id as the log file name, Stata would remove parent
@@ -115,12 +116,12 @@ def convert_task_id_to_name_of_log_file(id_):
     return converted_id
 
 
-def _to_list(scalar_or_iter):
+def _to_list(scalar_or_iter: Any) -> list[Any]:
     """Convert scalars and iterables to list.
 
     Parameters
     ----------
-    scalar_or_iter : str or list
+    scalar_or_iter
 
     Returns
     -------