diff --git a/README.md b/README.md
index 9515ad1..dda1797 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,8 @@
-# build-install-ca65-action
-Build and install the assembler components of cc65
+# Build & Install ca65 Action
+
+This action will build and install the cc65 assembler components (ca65, ld65).
+
+* The tip-of-tree version from https://github.com/cc65/cc65 is used.
+* Targets are built and installed, so later steps can use the `ca65` and `ld65` commands directly.
+
+The action has no inputs or outputs.
diff --git a/action.yml b/action.yml
new file mode 100644
index 0000000..89a38a4
--- /dev/null
+++ b/action.yml
@@ -0,0 +1,10 @@
+name: 'Build and Install cc65 Assembler Components'
+description: 'Builds and installs the cc65 assembler components (ca65, ld65)'
+runs:
+  using: "composite"
+  steps:
+    - run: >
+        git clone https://github.com/cc65/cc65 /tmp/cc65 &&
+        sudo make -C /tmp/cc65 ca65 ld65 avail &&
+        ca65 --version
+      shell: bash