diff --git a/src/Interpreters/UserDefinedFunctionFactory.h b/src/Interpreters/UserDefinedFunctionFactory.h
index b479d629532..0d7167eb1b7 100644
--- a/src/Interpreters/UserDefinedFunctionFactory.h
+++ b/src/Interpreters/UserDefinedFunctionFactory.h
@@ -10,19 +10,25 @@
 namespace DB
 {
 
+///Factory for user defined functions stores functions.
 class UserDefinedFunctionFactory : public IHints<1, UserDefinedFunctionFactory>
 {
 public:
     static UserDefinedFunctionFactory & instance();
 
+    /// Register function with function_name. create_function_query pointer must be ASTCreateFunctionQuery.
     void registerFunction(const String & function_name, ASTPtr create_function_query);
 
+    /// Unregister function with function_name.
     void unregisterFunction(const String & function_name);
 
+    /// Throws an exception if not found. Result ast pointer safely can be casted to ASTCreateFunctionQuery.
     ASTPtr get(const String & function_name) const;
 
+    /// Returns nullptr if not found. Result ast pointer safely can be casted to ASTCreateFunctionQuery.
     ASTPtr tryGet(const String & function_name) const;
 
+    /// Get all registered function names.
     std::vector<String> getAllRegisteredNames() const override;
 
 private: