diff --git a/.github/workflows/checks.yaml b/.github/workflows/checks.yaml
index 7e68fe0..d334574 100644
--- a/.github/workflows/checks.yaml
+++ b/.github/workflows/checks.yaml
@@ -15,9 +15,13 @@ jobs:
         uses: actions/setup-python@v5
         with:
           python-version: "3.12"
-      - name: Install requirements
-        run: pip install -r requirements_dev.txt
+      - name: Install poetry
+        run: pip install poetry
+      - name: Install dependencies
+        run: poetry install
       - name: Lint with pylint
-        run: pylint tests/tasks/*
+        run: poetry run pylint tests/tasks/* crypt4gh_middleware/*
       - name: Lint with ruff
-        run: ruff check tests/tasks/*
+        run: poetry run ruff check tests/tasks/* crypt4gh_middleware/*
+      - name: Type checking with mypy
+        run: poetry run mypy crypt4gh_middleware
diff --git a/.gitignore b/.gitignore
index 90f8fbb..aeda042 100644
--- a/.gitignore
+++ b/.gitignore
@@ -173,4 +173,6 @@ poetry.toml
 # LSP config files
 pyrightconfig.json
 
-# End of https://www.toptal.com/developers/gitignore/api/python
\ No newline at end of file
+# End of https://www.toptal.com/developers/gitignore/api/python
+
+outputs/
\ No newline at end of file
diff --git a/poetry.lock b/poetry.lock
index ee1d943..0a55cf9 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -397,6 +397,64 @@ files = [
     {file = "mccabe-0.7.0.tar.gz", hash = "sha256:348e0240c33b60bbdf4e523192ef919f28cb2c3d7d5c7794f74009290f236325"},
 ]
 
+[[package]]
+name = "mypy"
+version = "1.10.1"
+description = "Optional static typing for Python"
+optional = false
+python-versions = ">=3.8"
+files = [
+    {file = "mypy-1.10.1-cp310-cp310-macosx_10_9_x86_64.whl", hash = "sha256:e36f229acfe250dc660790840916eb49726c928e8ce10fbdf90715090fe4ae02"},
+    {file = "mypy-1.10.1-cp310-cp310-macosx_11_0_arm64.whl", hash = "sha256:51a46974340baaa4145363b9e051812a2446cf583dfaeba124af966fa44593f7"},
+    {file = "mypy-1.10.1-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:901c89c2d67bba57aaaca91ccdb659aa3a312de67f23b9dfb059727cce2e2e0a"},
+    {file = "mypy-1.10.1-cp310-cp310-musllinux_1_1_x86_64.whl", hash = "sha256:0cd62192a4a32b77ceb31272d9e74d23cd88c8060c34d1d3622db3267679a5d9"},
+    {file = "mypy-1.10.1-cp310-cp310-win_amd64.whl", hash = "sha256:a2cbc68cb9e943ac0814c13e2452d2046c2f2b23ff0278e26599224cf164e78d"},
+    {file = "mypy-1.10.1-cp311-cp311-macosx_10_9_x86_64.whl", hash = "sha256:bd6f629b67bb43dc0d9211ee98b96d8dabc97b1ad38b9b25f5e4c4d7569a0c6a"},
+    {file = "mypy-1.10.1-cp311-cp311-macosx_11_0_arm64.whl", hash = "sha256:a1bbb3a6f5ff319d2b9d40b4080d46cd639abe3516d5a62c070cf0114a457d84"},
+    {file = "mypy-1.10.1-cp311-cp311-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:b8edd4e9bbbc9d7b79502eb9592cab808585516ae1bcc1446eb9122656c6066f"},
+    {file = "mypy-1.10.1-cp311-cp311-musllinux_1_1_x86_64.whl", hash = "sha256:6166a88b15f1759f94a46fa474c7b1b05d134b1b61fca627dd7335454cc9aa6b"},
+    {file = "mypy-1.10.1-cp311-cp311-win_amd64.whl", hash = "sha256:5bb9cd11c01c8606a9d0b83ffa91d0b236a0e91bc4126d9ba9ce62906ada868e"},
+    {file = "mypy-1.10.1-cp312-cp312-macosx_10_9_x86_64.whl", hash = "sha256:d8681909f7b44d0b7b86e653ca152d6dff0eb5eb41694e163c6092124f8246d7"},
+    {file = "mypy-1.10.1-cp312-cp312-macosx_11_0_arm64.whl", hash = "sha256:378c03f53f10bbdd55ca94e46ec3ba255279706a6aacaecac52ad248f98205d3"},
+    {file = "mypy-1.10.1-cp312-cp312-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:6bacf8f3a3d7d849f40ca6caea5c055122efe70e81480c8328ad29c55c69e93e"},
+    {file = "mypy-1.10.1-cp312-cp312-musllinux_1_1_x86_64.whl", hash = "sha256:701b5f71413f1e9855566a34d6e9d12624e9e0a8818a5704d74d6b0402e66c04"},
+    {file = "mypy-1.10.1-cp312-cp312-win_amd64.whl", hash = "sha256:3c4c2992f6ea46ff7fce0072642cfb62af7a2484efe69017ed8b095f7b39ef31"},
+    {file = "mypy-1.10.1-cp38-cp38-macosx_10_9_x86_64.whl", hash = "sha256:604282c886497645ffb87b8f35a57ec773a4a2721161e709a4422c1636ddde5c"},
+    {file = "mypy-1.10.1-cp38-cp38-macosx_11_0_arm64.whl", hash = "sha256:37fd87cab83f09842653f08de066ee68f1182b9b5282e4634cdb4b407266bade"},
+    {file = "mypy-1.10.1-cp38-cp38-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:8addf6313777dbb92e9564c5d32ec122bf2c6c39d683ea64de6a1fd98b90fe37"},
+    {file = "mypy-1.10.1-cp38-cp38-musllinux_1_1_x86_64.whl", hash = "sha256:5cc3ca0a244eb9a5249c7c583ad9a7e881aa5d7b73c35652296ddcdb33b2b9c7"},
+    {file = "mypy-1.10.1-cp38-cp38-win_amd64.whl", hash = "sha256:1b3a2ffce52cc4dbaeee4df762f20a2905aa171ef157b82192f2e2f368eec05d"},
+    {file = "mypy-1.10.1-cp39-cp39-macosx_10_9_x86_64.whl", hash = "sha256:fe85ed6836165d52ae8b88f99527d3d1b2362e0cb90b005409b8bed90e9059b3"},
+    {file = "mypy-1.10.1-cp39-cp39-macosx_11_0_arm64.whl", hash = "sha256:c2ae450d60d7d020d67ab440c6e3fae375809988119817214440033f26ddf7bf"},
+    {file = "mypy-1.10.1-cp39-cp39-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:6be84c06e6abd72f960ba9a71561c14137a583093ffcf9bbfaf5e613d63fa531"},
+    {file = "mypy-1.10.1-cp39-cp39-musllinux_1_1_x86_64.whl", hash = "sha256:2189ff1e39db399f08205e22a797383613ce1cb0cb3b13d8bcf0170e45b96cc3"},
+    {file = "mypy-1.10.1-cp39-cp39-win_amd64.whl", hash = "sha256:97a131ee36ac37ce9581f4220311247ab6cba896b4395b9c87af0675a13a755f"},
+    {file = "mypy-1.10.1-py3-none-any.whl", hash = "sha256:71d8ac0b906354ebda8ef1673e5fde785936ac1f29ff6987c7483cfbd5a4235a"},
+    {file = "mypy-1.10.1.tar.gz", hash = "sha256:1f8f492d7db9e3593ef42d4f115f04e556130f2819ad33ab84551403e97dd4c0"},
+]
+
+[package.dependencies]
+mypy-extensions = ">=1.0.0"
+tomli = {version = ">=1.1.0", markers = "python_version < \"3.11\""}
+typing-extensions = ">=4.1.0"
+
+[package.extras]
+dmypy = ["psutil (>=4.0)"]
+install-types = ["pip"]
+mypyc = ["setuptools (>=50)"]
+reports = ["lxml"]
+
+[[package]]
+name = "mypy-extensions"
+version = "1.0.0"
+description = "Type system extensions for programs checked with the mypy type checker."
+optional = false
+python-versions = ">=3.5"
+files = [
+    {file = "mypy_extensions-1.0.0-py3-none-any.whl", hash = "sha256:4392f6c0eb8a5668a69e23d168ffa70f0be9ccfd32b5cc2d26a34ae5b844552d"},
+    {file = "mypy_extensions-1.0.0.tar.gz", hash = "sha256:75dbf8955dc00442a438fc4d0666508a9a97b6bd41aa2f0ffe9d2f2725af0782"},
+]
+
 [[package]]
 name = "packaging"
 version = "24.1"
@@ -689,4 +747,4 @@ zstd = ["zstandard (>=0.18.0)"]
 [metadata]
 lock-version = "2.0"
 python-versions = "^3.8"
-content-hash = "4a84ac7750beb1e822430addf3958ffd407ddb0cb797f99a395d817adc004eaf"
+content-hash = "eea7c3986781d6dbfbd758ea9e50847114fcceed370086e44a0f4a0423b59204"
diff --git a/pyproject.toml b/pyproject.toml
index ab486f1..1cbdd35 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -19,6 +19,7 @@ requests = "*"
 [tool.poetry.group.lint.dependencies]
 ruff = "*"
 pylint = "*"
+mypy = "*"
 
 [tool.pylint."MESSAGES CONTROL"]
 disable = ["logging-fstring-interpolation"]
diff --git a/requirements.txt b/requirements.txt
deleted file mode 100644
index 3f46541..0000000
--- a/requirements.txt
+++ /dev/null
@@ -1 +0,0 @@
-crypt4gh~=1.7
\ No newline at end of file
diff --git a/requirements_dev.txt b/requirements_dev.txt
deleted file mode 100644
index eca9e61..0000000
--- a/requirements_dev.txt
+++ /dev/null
@@ -1,4 +0,0 @@
-requests
-pytest
-pylint
-ruff