docs: show explicit startup activation in plugin examples

docs/plugins/building-plugins.md

@@ -76,6 +76,9 @@ and provider plugins have dedicated guides linked above.
       "id": "my-plugin",
       "name": "My Plugin",
       "description": "Adds a custom tool to OpenClaw",
+      "activation": {
+        "onStartup": true
+      },
       "configSchema": {
         "type": "object",
         "additionalProperties": false
@@ -84,7 +87,9 @@ and provider plugins have dedicated guides linked above.
     ```
     </CodeGroup>
 
-    Every plugin needs a manifest, even with no config. See
+    Every plugin needs a manifest, even with no config, and every plugin should
+    declare `activation.onStartup` intentionally. Runtime-registered tools need
+    startup import, so this example sets it to `true`. See
     [Manifest](/plugins/manifest) for the full schema. The canonical ClawHub
     publish snippets live in `docs/snippets/plugin-publish/`.
 

docs/snippets/plugin-publish/minimal-openclaw.plugin.json

@@ -2,6 +2,9 @@
   "id": "my-plugin",
   "name": "My Plugin",
   "description": "Adds a custom tool to OpenClaw",
+  "activation": {
+    "onStartup": true
+  },
   "configSchema": {
     "type": "object",
     "additionalProperties": false