diff --git a/bin/tools/named-rrchecker.rst b/bin/tools/named-rrchecker.rst
index 28da236b72..470f28fdd4 100644
--- a/bin/tools/named-rrchecker.rst
+++ b/bin/tools/named-rrchecker.rst
@@ -26,16 +26,25 @@ Synopsis
 Description
 ~~~~~~~~~~~
 
-:program:`named-rrchecker` reads a individual DNS resource record from standard
+:program:`named-rrchecker` reads a single DNS resource record (RR) from standard
 input and checks whether it is syntactically correct.
 
+The input format is a minimal subset of the DNS zone file format. The entire input must be:
+  CLASS TYPE RDATA
+
+* Input must not start with an owner (domain) name
+* The `CLASS` field is mandatory (typically ``IN``).
+* The `TTL` field **must not** be present.
+* RDATA format is specific to each RRTYPE.
+* Leading and trailing whitespace in each field is ignored.
+
+Format details can be found in :rfc:`1035#section-5.1` under ``<rr>``
+specification. :rfc:`3597` format is also accepted in any of the input fields.
+
+
 Options
 ~~~~~~~
 
-.. option:: -h
-
-   This option prints out the help menu.
-
 .. option:: -o origin
 
    This option specifies the origin to be used when interpreting
@@ -59,4 +68,4 @@ Options
 See Also
 ~~~~~~~~
 
-:rfc:`1034`, :rfc:`1035`, :iscman:`named(8) <named>`.
+:rfc:`1034`, :rfc:`1035`, :rfc:`3957`, :iscman:`named(8) <named>`.