diff --git a/identify/README.md b/identify/README.md
index 649053c6c..c31c3dc8c 100644
--- a/identify/README.md
+++ b/identify/README.md
@@ -94,12 +94,18 @@ protocol families / networks.
 
 Example value: `/my-network/0.1.0`.
 
+Implementations should discard non-ASCII characters and trim the string
+to 64 characters.
+
 ### agentVersion
 
 This is a free-form string, identifying the implementation of the peer.
 The usual format is `agent-name/version`, where `agent-name` is
 the name of the program or library and `version` is its semantic version.
 
+Implementations should discard non-ASCII characters and trim the string
+to 64 characters.
+
 ### publicKey
 
 This is the public key of the peer, marshalled in binary form as specicfied
@@ -125,6 +131,9 @@ observable source address.
 
 This is a list of protocols supported by the peer.
 
+Implementations should discard non-ASCII characters and trim each string
+to 64 characters.
+
 A node should only advertise a protocol if it's willing to receive inbound
 streams on that protocol. This is relevant for asymmetrical protocols. For
 example assume an asymmetrical request-response style protocol `foo` where some