diff --git a/README.md b/README.md
index 9ebefa9..095c361 100644
--- a/README.md
+++ b/README.md
@@ -20,6 +20,12 @@ finding.
 | Warning      | `SPF`, `A6`, `MD`, `MF`                                                                       | RFC 7208 / RFC 6563 / RFC 973: replaced by TXT, AAAA, MX.                                |
 | Informational| `WKS`, `MB`, `MG`, `MR`, `MINFO`, `NULL`, `GPOS`, `NSAP`, `NSAP-PTR`, `X25`, `ISDN`, `RT`, `ATMA`, `EID`, `NIMLOC`, `SINK`, `NINFO`, `RKEY` | Experimental or historical (RFC 1035, 1183, 1706, 1712, ...); safe to delete. |
 
+## Rules
+
+| Code              | Description                                                                                       | Severity            |
+|-------------------|---------------------------------------------------------------------------------------------------|---------------------|
+| `legacy_records`  | Detects DNS record types deprecated by the IETF and reports each occurrence with RFC references. | CRITICAL            |
+
 ## Tests
 
 `go test ./...` covers: