diff --git a/docs/rules/no-deprecated-api.md b/docs/rules/no-deprecated-api.md
index 288e831e..51a4a742 100644
--- a/docs/rules/no-deprecated-api.md
+++ b/docs/rules/no-deprecated-api.md
@@ -7,6 +7,8 @@
 Node has many deprecated API.
 The community is going to remove those API from Node in future, so we should not use those.
 
+This only supports the static apis, eg `Buffer.from` is supported, but `Buffer#includes` is not.
+
 ## 📖 Rule Details
 
 Examples of 👎 **incorrect** code for this rule:
diff --git a/docs/rules/no-unsupported-features/node-builtins.md b/docs/rules/no-unsupported-features/node-builtins.md
index d3bd2259..098f5a73 100644
--- a/docs/rules/no-unsupported-features/node-builtins.md
+++ b/docs/rules/no-unsupported-features/node-builtins.md
@@ -10,6 +10,8 @@ You can check [Node.js Documentation](https://nodejs.org/api/) to know which Nod
 This rule reports unsupported Node.js built-in APIs on the configured Node.js version as lint errors.
 Editor integrations of ESLint would be useful to know it in real-time.
 
+This only supports the static apis, eg `Buffer.from` is supported, but `Buffer#includes` is not.
+
 ## 📖 Rule Details
 
 This rule reports APIs of Node.js built-in APIs on the basis of [Node.js v13.2.0 Documentation](https://nodejs.org/docs/v13.2.0/api/).