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--- a/README.md
+++ b/README.md
@@ -1,15 +1,27 @@
 # GitHub Pull Request Plugin
 
-A [Buildkite plugin](https://buildkite.com/docs/agent/v3/plugins) to checkout the GitHub post-merge check PR ref (`refs/pull/123/merge`) rather than building the branch `HEAD`.
+A [Buildkite plugin](https://buildkite.com/docs/agent/v3/plugins) to help build the GitHub post-merge check PR ref (`refs/pull/123/merge`).
 
-This ensures tests run against the "merged" branch, helping catch bad merges.
+This plugin helps you run CI run against the "merged" branch, helping catch bad merges.
+
+The plugin has two modes:
+  - `mode: trigger` to async trigger another build (of the current pipeline); and
+  - `mode: checkout` to checkout the PR merged ref (`refs/pull/123/merge`) rather than the head (`refs/pull/123/head`)
 
 ## Example
 
 ```yml
 steps:
   - plugins:
-      zsims/github-merged-pr#v0.0.4: ~
+      zsims/github-merged-pr#v0.0.5:
+        mode: checkout
+```
+
+```yml
+steps:
+  - plugins:
+      zsims/github-merged-pr#v0.0.5:
+        mode: trigger
 ```
 
 Ensure `Skip pull request builds for existing commits` is set to `false` in your Pipeline settings, as BuildKite will build the branch and skip the PR build.