diff --git a/include/return_types.hpp b/include/answer.hpp
similarity index 92%
rename from include/return_types.hpp
rename to include/answer.hpp
index 65b8f6e..2eb05aa 100644
--- a/include/return_types.hpp
+++ b/include/answer.hpp
@@ -14,8 +14,8 @@
  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef MASTODONPP_RETURN_TYPES_HPP
-#define MASTODONPP_RETURN_TYPES_HPP
+#ifndef MASTODONPP_ANSWER_HPP
+#define MASTODONPP_ANSWER_HPP
 
 #include <cstdint>
 #include <string>
@@ -34,7 +34,7 @@ using std::string_view;
  *
  *  @since  0.1.0
  *
- *  @headerfile return_types.hpp mastodonpp/return_types.hpp
+ *  @headerfile answer.hpp mastodonpp/answer.hpp
  *
  */
 struct answer_type
@@ -103,4 +103,4 @@ struct answer_type
 
 } // namespace mastodonpp
 
-#endif  // MASTODONPP_RETURN_TYPES_HPP
+#endif  // MASTODONPP_ANSWER_HPP
diff --git a/include/connection.hpp b/include/connection.hpp
index a26120c..6e43bc6 100644
--- a/include/connection.hpp
+++ b/include/connection.hpp
@@ -17,10 +17,10 @@
 #ifndef MASTODONPP_CONNECTION_HPP
 #define MASTODONPP_CONNECTION_HPP
 
+#include "answer.hpp"
 #include "api.hpp"
 #include "curl_wrapper.hpp"
 #include "instance.hpp"
-#include "return_types.hpp"
 
 #include <string>
 #include <string_view>
diff --git a/include/curl_wrapper.hpp b/include/curl_wrapper.hpp
index 90e010a..267de96 100644
--- a/include/curl_wrapper.hpp
+++ b/include/curl_wrapper.hpp
@@ -17,18 +17,24 @@
 #ifndef MASTODONPP_CURL_WRAPPER_HPP
 #define MASTODONPP_CURL_WRAPPER_HPP
 
-#include "return_types.hpp"
+#include "answer.hpp"
 
 #include "curl/curl.h"
 
+#include <map>
 #include <string>
 #include <string_view>
+#include <variant>
+#include <vector>
 
 namespace mastodonpp
 {
 
+using std::map;
 using std::string;
 using std::string_view;
+using std::variant;
+using std::vector;
 
 /*!
  *  @brief  The HTTP method.
@@ -44,6 +50,22 @@ enum class http_method
     DELETE
 };
 
+/*!
+ *  @brief  std::map of parameters for API calls.
+ *
+ *  Example:
+ *  @code
+ *  parametermap parameters
+ *      {
+ *          {"id", "12"},
+ *          {"poll[options]", vector<string>{"Yes", "No", "Maybe"}}
+ *      };
+ *  @endcode
+ *
+ *  @since  0.1.0
+ */
+using parametermap = map<string, variant<string, vector<string>>>;
+
 /*!
  *  @brief  Handles the details of network connections.
  *
diff --git a/include/mastodonpp.hpp b/include/mastodonpp.hpp
index 70d9bdc..113ec0b 100644
--- a/include/mastodonpp.hpp
+++ b/include/mastodonpp.hpp
@@ -17,11 +17,11 @@
 #ifndef MASTODONPP_HPP
 #define MASTODONPP_HPP
 
+#include "answer.hpp"
 #include "api.hpp"
 #include "connection.hpp"
 #include "exceptions.hpp"
 #include "instance.hpp"
-#include "return_types.hpp"
 
 /*!
  *  @headerfile mastodonpp.hpp mastodonpp/mastodonpp.hpp
@@ -72,6 +72,8 @@
  *  Any unrecoverable libcurl error will be thrown as a
  *  mastodonpp::CURLException. Network errors will **not** be thrown, but
  *  reported via the return value.
+ *
+ *  @example example01_instance_info.cpp
  */
 
 /*!
diff --git a/src/return_types.cpp b/src/answer.cpp
similarity index 97%
rename from src/return_types.cpp
rename to src/answer.cpp
index 8dd25ff..8006f90 100644
--- a/src/return_types.cpp
+++ b/src/answer.cpp
@@ -14,7 +14,7 @@
  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "return_types.hpp"
+#include "answer.hpp"
 
 namespace mastodonpp
 {
diff --git a/src/instance.cpp b/src/instance.cpp
index b367f9b..683e20e 100644
--- a/src/instance.cpp
+++ b/src/instance.cpp
@@ -14,9 +14,9 @@
  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include "answer.hpp"
 #include "instance.hpp"
 #include "log.hpp"
-#include "return_types.hpp"
 
 namespace mastodonpp
 {
diff --git a/src/log.hpp b/src/log.hpp
index ab8c033..286cd07 100644
--- a/src/log.hpp
+++ b/src/log.hpp
@@ -26,6 +26,7 @@ namespace mastodonpp
 using std::cerr;
 using std::string_view;
 
+//! @private
 constexpr auto shorten_filename(const string_view &filename)
 {
     for (const string_view &dir : {"/src/", "/include/"})