diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index 1aa29fa3f7..81397668e8 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -655,9 +655,11 @@ inline uint32_t fnv1_hash_object_id(const char *str, size_t len) {
 }
 
 /// snprintf-like function returning std::string of maximum length \p len (excluding null terminator).
+/// @warning Allocates heap memory. Use snprintf() with a stack buffer instead.
 std::string __attribute__((format(printf, 1, 3))) str_snprintf(const char *fmt, size_t len, ...);
 
 /// sprintf-like function returning std::string.
+/// @warning Allocates heap memory. Use snprintf() with a stack buffer instead.
 std::string __attribute__((format(printf, 1, 2))) str_sprintf(const char *fmt, ...);
 
 #ifdef USE_ESP8266
diff --git a/script/ci-custom.py b/script/ci-custom.py
index 01e197057a..b146c9867e 100755
--- a/script/ci-custom.py
+++ b/script/ci-custom.py
@@ -692,6 +692,8 @@ HEAP_ALLOCATING_HELPERS = {
     "str_truncate": "removal (function is unused)",
     "str_upper_case": "removal (function is unused)",
     "str_snake_case": "removal (function is unused)",
+    "str_sprintf": "snprintf() with a stack buffer",
+    "str_snprintf": "snprintf() with a stack buffer",
 }
 
 
@@ -710,7 +712,9 @@ HEAP_ALLOCATING_HELPERS = {
     r"str_sanitize(?!_)|"
     r"str_truncate|"
     r"str_upper_case|"
-    r"str_snake_case"
+    r"str_snake_case|"
+    r"str_sprintf|"
+    r"str_snprintf"
     r")\s*\(" + CPP_RE_EOL,
     include=cpp_include,
     exclude=[