diff --git a/proto/protocol.xml b/proto/protocol.xml
index 3332d24..bf77176 100644
--- a/proto/protocol.xml
+++ b/proto/protocol.xml
@@ -1731,7 +1731,7 @@
       </description>
     </request>
 
-    <request name="bind_tool_capabilities" since="1">
+    <request name="bind_tool_capabilities" since="1" context-type="sender">
       <description summary="stylus tool capability bind request">
         Request to bind to a given set of tool capabilities. This is used
         by clients to describe which subset of server-supported capabilities
@@ -2032,7 +2032,10 @@
 
         The server sends this event after attaching the ei_stylus interface
         to an ei_device. This event describes the set of capabilities that
-        the server is willing to let the client to bind to.
+        the tool supports. For sender contexts, the client must confirm
+        (and optionally narrow down) the capabilities with the
+        ei_stylus.bind_tool_capabilities request before the device will
+        send events.
       </description>
       <arg name="capabilities" type="uint32" enum="capability" summary="A capability mask for the events available through this interface"/>
     </event>