fix: update readme

Author: martinal

README.md

@@ -19,6 +19,7 @@ Then configure your LLM client (e.g. Claude Desktop or Cursor), like this:
     "myDatabuttonApp": {
       "command": "uvx",
       "args": [
+        "-U",
         "databutton-app-mcp"
       ],
       "env": {
@@ -29,6 +30,27 @@ Then configure your LLM client (e.g. Claude Desktop or Cursor), like this:
 }
 ```
 
-Here DATABUTTON_API_KEY is either the api key or the path to a file containing it.
+or this
+
+```json
+{
+  "mcpServers": {
+    "myDatabuttonApp": {
+      "command": "uvx",
+      "args": [
+        "-U",
+        "databutton-app-mcp",
+        "-k",
+        "/path/to/apikey.txt"
+      ]
+    }
+  }
+}
+```
+
+Here /path/to/apikey.txt is the full path to a file containing the api key,
+or DATABUTTON_API_KEY is either the api key value or the path to a file containing it.
 You can download the API key for your Databutton app on the app settings page.
 Make sure to keep it secure and don't share it.
+
+Note: This is early stage software. The -U flag to uvx make sure you always get the latest version of the tool.