diff --git a/setup-action/README.md b/setup-action/README.md
new file mode 100644
index 0000000..57eb0c1
--- /dev/null
+++ b/setup-action/README.md
@@ -0,0 +1,19 @@
+# kivikakk/niar/setup-action
+
+Use after cloning your project repository. You'll need to specify Niar as a
+dependency, and any HEAD versions of Amaranth et al. needed.
+
+Usage:
+
+```yaml
+- uses: kivikakk/niar/setup-action@main
+  with:
+    install-oss-cad-suite: true
+    github-token: ${{ secrets.GITHUB_TOKEN }}
+    install-zig: 0.13.0
+```
+
+* Installs Python and PDM.
+* Runs `pdm install`.
+* If `install-oss-cad-suite` is specified, installs OSS CAD Suite using `github-token`.
+* If `install-zig` is specified, installs given version of Zig.
diff --git a/setup-action/action.yml b/setup-action/action.yml
index a1c8a3c..5cd6239 100644
--- a/setup-action/action.yml
+++ b/setup-action/action.yml
@@ -13,36 +13,11 @@ inputs:
 runs:
   using: composite
   steps:
-  - name: Checkout Niar
-    uses: actions/checkout@v4
-    with:
-      repository: kivikakk/niar
-      path: setup-niar-out/niar
+  - name: Setup PDM
+    uses: pdm-project/setup-pdm@v4
 
-  - name: Install Python 3.12
-    uses: actions/setup-python@v5
-    with:
-      python-version: '3.12'
-      cache: pip
-
-  - name: Install client repo pip dependencies
-    run: pip install --editable .
-    shell: bash
-
-  - name: Install pytest
-    run: pip install pytest pytest-xdist
-    shell: bash
-
-  - name: Install niar
-    run: cd setup-niar-out/niar && pip install -e .
-    shell: bash
-
-  - name: Install amaranth-stdio
-    run: pip install --no-deps git+https://github.com/amaranth-lang/amaranth-stdio.git
-    shell: bash
-
-  - name: Install amaranth-boards
-    run: pip install --no-deps git+https://github.com/amaranth-lang/amaranth-boards.git
+  - name: Install Python dependencies
+    run: pdm install
     shell: bash
 
   - name: Install OSS CAD Suite