diff --git a/tracker/tracker-mobx/README.md b/tracker/tracker-mobx/README.md
index 3011a1395..b054247ec 100644
--- a/tracker/tracker-mobx/README.md
+++ b/tracker/tracker-mobx/README.md
@@ -1,5 +1,6 @@
 # OpenReplay Tracker MobX plugin
-A MobX plugin for OpenReplay Tracker. This plugin allows you to see the MobX events during session replay.
+A MobX plugin for OpenReplay Tracker. 
+This plugin allows you to see the MobX events during session replay.
 
 ## Installation
 ```bash
@@ -8,7 +9,7 @@ npm i @openreplay/tracker-mobx
 
 ## Usage
 Initialize the `@openreplay/tracker` package as usual and load the plugin into it.
-Then put the generated middleware into your Redux chain.
+Then put is as a second argument to `observe` function from `mobx` package.
 
 ```js
 import Tracker from '@openreplay/tracker';
@@ -27,8 +28,8 @@ Options:
 
 ```js
 interface Options {
-    predicate?: (ev: { type: string; name: string; object: any; debugObjectName: string }) => boolean;
-    sanitize?: (ev: { state: any; type: string; property: string }) => { state: any; type: string; property: string };
+    predicate?: (observeEvent: { type: string; name: string; object: any; debugObjectName: string }) => boolean;
+    sanitize?: (resultAction: { state: any; type: string; property: string }) => { state: any; type: string; property: string };
     update?: boolean;
     add?: boolean;
     delete?: boolean;
@@ -41,3 +42,4 @@ trackerMobX({
 ```
 
 Where `predicate` can be used to dynamically turn off capturing and `sanitize` can be used to modify the payload before sending it to backend.
+Most of the actions fall into `update` type, refer to mobx documentation for more details about add and delete (mostly for Maps)
\ No newline at end of file
diff --git a/tracker/tracker-mobx/package.json b/tracker/tracker-mobx/package.json
index a068278e3..64e197a66 100644
--- a/tracker/tracker-mobx/package.json
+++ b/tracker/tracker-mobx/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@openreplay/tracker-mobx",
   "description": "Tracker plugin for MobX events recording",
-  "version": "4.0.0",
+  "version": "4.0.1",
   "keywords": [
     "mobx",
     "logging",