diff --git a/README.md b/README.md
index 1766e45..7c08bcf 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,16 @@ Lodestone helps you navigate the Fediverse.
 
 It gives you a tool to quickly search through your favorite posts, and helps you rediscover the things you found relevant.
 
+## Fediverse Software Compatibility
+
+The software is actively being tested against [Mastodon](https://docs.joinmastodon.org/) and compatible forks like [Hometown](https://github.com/hometown-fork/hometown/). The API surface that's used by this tool is quite small at the moment:
+
+- `POST /api/v1/apps`
+- `POST /oauth/token`
+- `GET /api/v1/favourites`
+
+It is tested to work with `Note` activities. Even though other activites are currently not tested, any effort to improve compatibility is welcome.
+
 ## Building a release
 
 Before anything, make sure JS dependencies are installed: