diff --git a/README.md b/README.md
index a53c8cf..ea5e0f4 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,18 @@ A GitHub Action to remove a milestone by the milestone's name
 If the milestone should fail if the provided milestone is missing<br> Default:
 false
 
+## Environment Variables
+
+### `GITHUB_TOKEN`
+
+**Required** The access token with which the Action does the authentication with
+GitHub
+
+### `CLOSE_MILESTONE_REPOSITORY`
+
+If provided, this variable overrides the repository used to close the milestone
+for. It has to be provided in the format of `<owner>/<repository name>`
+
 ## Outputs
 
 ### `milestone_id`