diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 0000000..ca6734f
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,19 @@
+# Random information that may be useful to contributors
+
+## Custom Matrix types
+
+- `eu.steffo.meta.twom.party`: room type used to distinguish TwoM parties from regular rooms, which are hidden.
+- `eu.steffo.meta.twom.rsvp`: state event type used for the user's response to a party invitation; uses the replying user's mxid as state key, and has an object with the following keys as payload:
+  - `eu.steffo.meta.twom.answer`: a string containing one of these values, indicating the user's presence at the party:
+    - `"SURE"`
+    - `"LATER"`
+    - `"MAYBE"`
+    - `"NOWAY"`
+    - `""`
+  - `eu.steffo.meta.twom.comment`: a string containing an user's freeform comment provided in addition to the answer.
+
+## Known issues
+
+- Avatar URLs are sometimes fetched before they're available on the homeserver, causing them not to be loaded correctly on party creation.
+- Due to API limitations, the app does not check if the user has permissions to perform certain actions, such as changing the name of a party, and instead returns a `MatrixError` when the action is attempted.
+- Due to Matrix protocol limitations, any user can change other users' party replies by sending custom state events, even though this app itself does not allow it.
diff --git a/app/src/main/java/eu/steffo/twom/matrix/utils/TwoMMatrix.kt b/app/src/main/java/eu/steffo/twom/matrix/utils/TwoMMatrix.kt
index 59fae2a..a3cda84 100644
--- a/app/src/main/java/eu/steffo/twom/matrix/utils/TwoMMatrix.kt
+++ b/app/src/main/java/eu/steffo/twom/matrix/utils/TwoMMatrix.kt
@@ -78,11 +78,11 @@ object TwoMMatrix {
         session.close()
     }
 
-    const val ROOM_TYPE = "eu.steffo.twom.happening"
+    const val ROOM_TYPE = "eu.steffo.meta.twom.party"
 
-    const val RSVP_STATE_TYPE = "eu.steffo.twom.rsvp"
+    const val RSVP_STATE_TYPE = "eu.steffo.meta.twom.rsvp"
 
-    const val RSVP_STATE_ANSWER_FIELD = "answer"
+    const val RSVP_STATE_ANSWER_FIELD = "eu.steffo.meta.twom.answer"
 
-    const val RSVP_STATE_COMMENT_FIELD = "comment"
+    const val RSVP_STATE_COMMENT_FIELD = "eu.steffo.meta.twom.comment"
 }
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