diff --git a/wizard-work/beam/json_canonical.py b/wizard-work/beam/json_canonical.py
index 5998392..4699aa6 100644
--- a/wizard-work/beam/json_canonical.py
+++ b/wizard-work/beam/json_canonical.py
@@ -1,5 +1,17 @@
-"""Canonical JSON serialization (RFC 8785-ish): sorted keys, compact separators,
-no NaN/Infinity, deterministic float repr, UTF-8, ensure_ascii=False."""
+"""Canonical JSON serialization: sorted keys, compact separators, no NaN/Infinity,
+deterministic float repr, UTF-8, ensure_ascii=False.
+
+NOT RFC 8785 (JCS), and not claimed to be. JCS is IEEE-754 double-based with its
+own number grammar; this module emits Python's `repr` for floats and passes int
+through unchanged. Three measured divergences from RFC 8785 Table 1:
+
+    -0.0    -> "-0.0"                (JCS: "0")
+    1e-06   -> "1e-06"               (JCS: "0.000001")
+    2**53+1 -> "9007199254740993"    (JCS max positive integer: 9007199254740992)
+
+Key order is `sort_keys=True`, i.e. by Unicode code point; JCS sorts by UTF-16
+code unit, so the two diverge above U+FFFF.
+"""
 from __future__ import annotations
 import json
 import math