diff --git a/README.md b/README.md
index 5590c51..2f90adf 100644
--- a/README.md
+++ b/README.md
@@ -367,6 +367,32 @@ Example:
 }
 ```
 
+### Special GDD Type: "Invoke Action"
+
+Some templates support invoking custom functions during their life-time.
+This GDD Type should be rendered as a Button in the GUI so that the user can click it to invoke the action.
+
+
+Example:
+```typescript
+{
+  "title": string, // [Mandatory] A short title / label of the action
+  "description": "", // [Optional] A longer description of the action
+  "type": "null",
+  "gddType": "invoke-action",
+  "gddOptions": {
+    // [mandatory] The script to execute/invoke in the template
+    // Example: "myCustomHello(\"world\", $path)"
+    "invoke": string
+  }
+}
+```
+
+Note: `$path` is a special token which will be substituted at runtime with the [JSONPath](https://goessner.net/articles/JsonPath/) of the action.
+This is useful when having an action inside an array, since this would cause multiple actions to render (one per row in the data).
+An example of a path would be `myData.people[2]` for the action in the 3rd row of an array called `people` in an object called `myData`.
+
+
 ## For GUI Developers
 
 When implementing a GUI to support the GDD definitions, you don't have to implement support for all GDD Types - since the GDD Types are designed to degrade gracefully. The only types that are mandatory to implement are the basic types `"boolean"`, `"string"`, `"number"`, `"integer"`, `"array"`and `"object"`.
@@ -392,6 +418,7 @@ function determineComponent(prop) {
   if (basicType === "integer") return componentInteger(prop);
   if (basicType === "array") return componentArray(prop);
   if (basicType === "object") return componentObject(prop);
+  if (basicType === "null") return null
 
   return null;
 }