diff --git a/src/clj/com/rpl/specter/protocols.cljx b/src/clj/com/rpl/specter/protocols.cljx
index b448a9d..8ccbfc8 100644
--- a/src/clj/com/rpl/specter/protocols.cljx
+++ b/src/clj/com/rpl/specter/protocols.cljx
@@ -1,8 +1,20 @@
 (ns com.rpl.specter.protocols)
 
 (defprotocol Navigator
-  (select* [this structure next-fn])
-  (transform* [this structure next-fn]))
+  (select* [this structure next-fn]
+    "An implementation of `select*` must call `next-fn` on each
+     subvalue of `structure`. The result of `select*` is specified
+     as follows:
+
+     1. `NONE` if `next-fn` never called
+     2. `NONE` if all calls to `next-fn` return `NONE`
+     3. Otherwise, any non-`NONE` return value from calling `next-fn`
+     ")
+  (transform* [this structure next-fn]
+    "An implementation of `transform*` must use `next-fn` to transform
+     any subvalues of `structure` and then merge those transformed values
+     back into `structure`. Everything else in `structure` must be unchanged."
+    ))
 
 (defprotocol Collector
   (collect-val [this structure]))