diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
new file mode 100644
index 0000000..ced8ee7
--- /dev/null
+++ b/.github/workflows/lint.yml
@@ -0,0 +1,43 @@
+name: Lint and Type Check
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  lint-and-typecheck:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.13"]
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v5
+      with:
+        python-version: ${{ matrix.python-version }}
+
+    - name: Install uv
+      uses: astral-sh/setup-uv@v3
+      with:
+        version: "latest"
+
+    - name: Install dependencies
+      run: |
+        uv sync --extra 'dev'
+
+    - name: Run ruff check
+      run: |
+        uv run ruff check .
+
+    - name: Run ruff format check
+      run: |
+        uv run ruff format --check .
+
+    - name: Run mypy
+      run: |
+        uv run mypy .
diff --git a/pyproject.toml b/pyproject.toml
index be2bada..f28fcf1 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -12,6 +12,7 @@ dependencies = [
 [project.optional-dependencies]
 dev = [
     "httpx>=0.28.1",
+    "mypy>=1.14.0",
     "pyright>=1.1.401",
     "pytest>=8.3.5",
     "pytest-asyncio>=1.0.0",
diff --git a/uv.lock b/uv.lock
index 06d52af..1c2570d 100644
--- a/uv.lock
+++ b/uv.lock
@@ -579,6 +579,41 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/b3/38/89ba8ad64ae25be8de66a6d463314cf1eb366222074cfda9ee839c56a4b4/mdurl-0.1.2-py3-none-any.whl", hash = "sha256:84008a41e51615a49fc9966191ff91509e3c40b939176e643fd50a5c2196b8f8", size = 9979, upload-time = "2022-08-14T12:40:09.779Z" },
 ]
 
+[[package]]
+name = "mypy"
+version = "1.18.2"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "mypy-extensions" },
+    { name = "pathspec" },
+    { name = "typing-extensions" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/c0/77/8f0d0001ffad290cef2f7f216f96c814866248a0b92a722365ed54648e7e/mypy-1.18.2.tar.gz", hash = "sha256:06a398102a5f203d7477b2923dda3634c36727fa5c237d8f859ef90c42a9924b", size = 3448846, upload-time = "2025-09-19T00:11:10.519Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/5f/04/7f462e6fbba87a72bc8097b93f6842499c428a6ff0c81dd46948d175afe8/mypy-1.18.2-cp313-cp313-macosx_10_13_x86_64.whl", hash = "sha256:07b8b0f580ca6d289e69209ec9d3911b4a26e5abfde32228a288eb79df129fcc", size = 12898728, upload-time = "2025-09-19T00:10:01.33Z" },
+    { url = "https://files.pythonhosted.org/packages/99/5b/61ed4efb64f1871b41fd0b82d29a64640f3516078f6c7905b68ab1ad8b13/mypy-1.18.2-cp313-cp313-macosx_11_0_arm64.whl", hash = "sha256:ed4482847168439651d3feee5833ccedbf6657e964572706a2adb1f7fa4dfe2e", size = 11910758, upload-time = "2025-09-19T00:10:42.607Z" },
+    { url = "https://files.pythonhosted.org/packages/3c/46/d297d4b683cc89a6e4108c4250a6a6b717f5fa96e1a30a7944a6da44da35/mypy-1.18.2-cp313-cp313-manylinux2014_aarch64.manylinux_2_17_aarch64.manylinux_2_28_aarch64.whl", hash = "sha256:c3ad2afadd1e9fea5cf99a45a822346971ede8685cc581ed9cd4d42eaf940986", size = 12475342, upload-time = "2025-09-19T00:11:00.371Z" },
+    { url = "https://files.pythonhosted.org/packages/83/45/4798f4d00df13eae3bfdf726c9244bcb495ab5bd588c0eed93a2f2dd67f3/mypy-1.18.2-cp313-cp313-manylinux2014_x86_64.manylinux_2_17_x86_64.manylinux_2_28_x86_64.whl", hash = "sha256:a431a6f1ef14cf8c144c6b14793a23ec4eae3db28277c358136e79d7d062f62d", size = 13338709, upload-time = "2025-09-19T00:11:03.358Z" },
+    { url = "https://files.pythonhosted.org/packages/d7/09/479f7358d9625172521a87a9271ddd2441e1dab16a09708f056e97007207/mypy-1.18.2-cp313-cp313-musllinux_1_2_x86_64.whl", hash = "sha256:7ab28cc197f1dd77a67e1c6f35cd1f8e8b73ed2217e4fc005f9e6a504e46e7ba", size = 13529806, upload-time = "2025-09-19T00:10:26.073Z" },
+    { url = "https://files.pythonhosted.org/packages/71/cf/ac0f2c7e9d0ea3c75cd99dff7aec1c9df4a1376537cb90e4c882267ee7e9/mypy-1.18.2-cp313-cp313-win_amd64.whl", hash = "sha256:0e2785a84b34a72ba55fb5daf079a1003a34c05b22238da94fcae2bbe46f3544", size = 9833262, upload-time = "2025-09-19T00:10:40.035Z" },
+    { url = "https://files.pythonhosted.org/packages/5a/0c/7d5300883da16f0063ae53996358758b2a2df2a09c72a5061fa79a1f5006/mypy-1.18.2-cp314-cp314-macosx_10_13_x86_64.whl", hash = "sha256:62f0e1e988ad41c2a110edde6c398383a889d95b36b3e60bcf155f5164c4fdce", size = 12893775, upload-time = "2025-09-19T00:10:03.814Z" },
+    { url = "https://files.pythonhosted.org/packages/50/df/2cffbf25737bdb236f60c973edf62e3e7b4ee1c25b6878629e88e2cde967/mypy-1.18.2-cp314-cp314-macosx_11_0_arm64.whl", hash = "sha256:8795a039bab805ff0c1dfdb8cd3344642c2b99b8e439d057aba30850b8d3423d", size = 11936852, upload-time = "2025-09-19T00:10:51.631Z" },
+    { url = "https://files.pythonhosted.org/packages/be/50/34059de13dd269227fb4a03be1faee6e2a4b04a2051c82ac0a0b5a773c9a/mypy-1.18.2-cp314-cp314-manylinux2014_aarch64.manylinux_2_17_aarch64.manylinux_2_28_aarch64.whl", hash = "sha256:6ca1e64b24a700ab5ce10133f7ccd956a04715463d30498e64ea8715236f9c9c", size = 12480242, upload-time = "2025-09-19T00:11:07.955Z" },
+    { url = "https://files.pythonhosted.org/packages/5b/11/040983fad5132d85914c874a2836252bbc57832065548885b5bb5b0d4359/mypy-1.18.2-cp314-cp314-manylinux2014_x86_64.manylinux_2_17_x86_64.manylinux_2_28_x86_64.whl", hash = "sha256:d924eef3795cc89fecf6bedc6ed32b33ac13e8321344f6ddbf8ee89f706c05cb", size = 13326683, upload-time = "2025-09-19T00:09:55.572Z" },
+    { url = "https://files.pythonhosted.org/packages/e9/ba/89b2901dd77414dd7a8c8729985832a5735053be15b744c18e4586e506ef/mypy-1.18.2-cp314-cp314-musllinux_1_2_x86_64.whl", hash = "sha256:20c02215a080e3a2be3aa50506c67242df1c151eaba0dcbc1e4e557922a26075", size = 13514749, upload-time = "2025-09-19T00:10:44.827Z" },
+    { url = "https://files.pythonhosted.org/packages/25/bc/cc98767cffd6b2928ba680f3e5bc969c4152bf7c2d83f92f5a504b92b0eb/mypy-1.18.2-cp314-cp314-win_amd64.whl", hash = "sha256:749b5f83198f1ca64345603118a6f01a4e99ad4bf9d103ddc5a3200cc4614adf", size = 9982959, upload-time = "2025-09-19T00:10:37.344Z" },
+    { url = "https://files.pythonhosted.org/packages/87/e3/be76d87158ebafa0309946c4a73831974d4d6ab4f4ef40c3b53a385a66fd/mypy-1.18.2-py3-none-any.whl", hash = "sha256:22a1748707dd62b58d2ae53562ffc4d7f8bcc727e8ac7cbc69c053ddc874d47e", size = 2352367, upload-time = "2025-09-19T00:10:15.489Z" },
+]
+
+[[package]]
+name = "mypy-extensions"
+version = "1.1.0"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/a2/6e/371856a3fb9d31ca8dac321cda606860fa4548858c0cc45d9d1d4ca2628b/mypy_extensions-1.1.0.tar.gz", hash = "sha256:52e68efc3284861e772bbcd66823fde5ae21fd2fdb51c62a211403730b916558", size = 6343, upload-time = "2025-04-22T14:54:24.164Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/79/7b/2c79738432f5c924bef5071f933bcc9efd0473bac3b4aa584a6f7c1c8df8/mypy_extensions-1.1.0-py3-none-any.whl", hash = "sha256:1be4cccdb0f2482337c4743e60421de3a356cd97508abadd57d47403e94f5505", size = 4963, upload-time = "2025-04-22T14:54:22.983Z" },
+]
+
 [[package]]
 name = "narwhals"
 version = "1.41.1"
@@ -684,6 +719,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/39/c2/646d2e93e0af70f4e5359d870a63584dacbc324b54d73e6b3267920ff117/pandas-2.3.0-cp313-cp313t-musllinux_1_2_x86_64.whl", hash = "sha256:bb3be958022198531eb7ec2008cfc78c5b1eed51af8600c6c5d9160d89d8d249", size = 13231847, upload-time = "2025-06-05T03:27:51.465Z" },
 ]
 
+[[package]]
+name = "pathspec"
+version = "0.12.1"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/ca/bc/f35b8446f4531a7cb215605d100cd88b7ac6f44ab3fc94870c120ab3adbf/pathspec-0.12.1.tar.gz", hash = "sha256:a482d51503a1ab33b1c67a6c3813a26953dbdc71c31dacaef9a838c4e29f5712", size = 51043, upload-time = "2023-12-10T22:30:45Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/cc/20/ff623b09d963f88bfde16306a54e12ee5ea43e9b597108672ff3a408aad6/pathspec-0.12.1-py3-none-any.whl", hash = "sha256:a0d503e138a4c123b27490a4f7beda6a01c6f288df0e4a8b79c7eb0dc7b4cc08", size = 31191, upload-time = "2023-12-10T22:30:43.14Z" },
+]
+
 [[package]]
 name = "pillow"
 version = "11.2.1"
@@ -808,6 +852,7 @@ dependencies = [
 [package.optional-dependencies]
 all = [
     { name = "httpx" },
+    { name = "mypy" },
     { name = "pyright" },
     { name = "pytest" },
     { name = "pytest-asyncio" },
@@ -822,6 +867,7 @@ client = [
 ]
 dev = [
     { name = "httpx" },
+    { name = "mypy" },
     { name = "pyright" },
     { name = "pytest" },
     { name = "pytest-asyncio" },
@@ -834,6 +880,7 @@ requires-dist = [
     { name = "fastapi", extras = ["all"], specifier = ">=0.115.12" },
     { name = "httpx", marker = "extra == 'dev'", specifier = ">=0.28.1" },
     { name = "langchain-google-genai", specifier = ">=2.1.5" },
+    { name = "mypy", marker = "extra == 'dev'", specifier = ">=1.14.0" },
     { name = "pyconjp2025-camp-tutorial", extras = ["client"], marker = "extra == 'all'" },
     { name = "pyconjp2025-camp-tutorial", extras = ["dev"], marker = "extra == 'all'" },
     { name = "pyright", marker = "extra == 'dev'", specifier = ">=1.1.401" },