diff --git a/esphome/core/helpers.h b/esphome/core/helpers.h
index 864fd92ffc..3782875dcf 100644
--- a/esphome/core/helpers.h
+++ b/esphome/core/helpers.h
@@ -190,7 +190,9 @@ template<typename T> class FixedVector {
     }
   }
 
-  // Add element (no reallocation - must have initialized capacity)
+  /// Add element without bounds checking
+  /// Caller must ensure sufficient capacity was allocated via init()
+  /// Silently ignores pushes beyond capacity to avoid runtime overhead
   void push_back(const T &value) {
     if (size_ < capacity_) {
       data_[size_++] = value;
@@ -199,6 +201,8 @@ template<typename T> class FixedVector {
 
   size_t size() const { return size_; }
 
+  /// Access element without bounds checking (matches std::vector behavior)
+  /// Caller must ensure index is valid (i < size())
   T &operator[](size_t i) { return data_[i]; }
   const T &operator[](size_t i) const { return data_[i]; }
 };