docs(adk): audit foundations and concept pages

adk/concepts/actions.mdx

@@ -2,7 +2,7 @@
 title: Actions
 ---
 
-Actions are callable functions that can be invoked by workflows, conversations, or other actions. They encapsulate reusable logic and can be called from anywhere in your agent.
+Actions are callable functions that can be invoked by workflows, conversations, other actions, and external API clients. They encapsulate reusable logic and can be called from anywhere in your agent.
 
 ## Creating an action
 
@@ -81,15 +81,18 @@ export default new Trigger({
 });
 ```
 
-```ts From a tool highlight={1,6}
-import { Autonomous, actions } from "@botpress/runtime"
+```ts From a tool highlight={1,8}
+import { Autonomous, actions, z } from "@botpress/runtime"
 
 export default new Autonomous.Tool({
     name: "someTool",
+    description: "A tool that does something",
+    input: z.object({}),
+    output: z.object({ result: z.string() }),
     handler: async () => {
         const result = await actions.doSomething()
-    }
-    // Other logic
+        return { result }
+    },
 })
 ```