diff --git a/src/strings.cpp b/src/strings.cpp
--- a/src/strings.cpp
+++ b/src/strings.cpp
@@ -35,8 +35,8 @@
 #include "table/strings.h"
 #include "table/control_codes.h"
 
-DynamicLanguages _dynlang;
-uint64 _decode_parameters[20];
+DynamicLanguages _dynlang;     ///< Language information of the program.
+uint64 _decode_parameters[20]; ///< Global array of string parameters. To access, use #SetDParam.
 
 static char *StationGetSpecialString(char *buff, int x, const char *last);
 static char *GetSpecialTownNameString(char *buff, int ind, uint32 seed, const char *last);
@@ -171,6 +171,10 @@ void SetDParamStr(uint n, const char *st
 	SetDParam(n, (uint64)(size_t)str);
 }
 
+/**
+ * Shift the string parameters in the global string parameter array by \a amount positions, making room at the beginning.
+ * @param amount Number of positions to shift.
+ */
 void InjectDParam(uint amount)
 {
 	assert((uint)amount < lengthof(_decode_parameters));
diff --git a/src/strings_func.h b/src/strings_func.h
--- a/src/strings_func.h
+++ b/src/strings_func.h
@@ -13,11 +13,22 @@ const char *GetStringPtr(StringID string
 
 void InjectDParam(uint amount);
 
+/**
+ * Set a string parameter \a v at index \a n in a given array \a s.
+ * @param s Array of string parameters.
+ * @param n Index of the string parameter.
+ * @param v Value of the string parameter.
+ */
 static inline void SetDParamX(uint64 *s, uint n, uint64 v)
 {
 	s[n] = v;
 }
 
+/**
+ * Set a string parameter \a v at index \a n in the global string parameter array.
+ * @param n Index of the string parameter.
+ * @param v Value of the string parameter.
+ */
 static inline void SetDParam(uint n, uint64 v)
 {
 	extern uint64 _decode_parameters[20];
@@ -28,11 +39,23 @@ static inline void SetDParam(uint n, uin
 
 void SetDParamStr(uint n, const char *str);
 
+/**
+ * Get the current string parameter at index \a n from parameter array \a s.
+ * @param s Array of string parameters.
+ * @param n Index of the string parameter.
+ * @return Value of the requested string parameter.
+ */
 static inline uint64 GetDParamX(const uint64 *s, uint n)
 {
 	return s[n];
 }
 
+/**
+ * Get the current string parameter at index \a n from the global string parameter array.
+ * @param s Array of string parameters.
+ * @param n Index of the string parameter.
+ * @return Value of the requested string parameter.
+ */
 static inline uint64 GetDParam(uint n)
 {
 	extern uint64 _decode_parameters[20];
@@ -41,12 +64,24 @@ static inline uint64 GetDParam(uint n)
 	return _decode_parameters[n];
 }
 
+/**
+ * Copy \a num string parameters from array \a src into the global string parameter array.
+ * @param offs Index in the global array to copy the first string parameter to.
+ * @param src  Source array of string parameters.
+ * @param num  Number of string parameters to copy.
+ */
 static inline void CopyInDParam(int offs, const uint64 *src, int num)
 {
 	extern uint64 _decode_parameters[20];
 	memcpy(_decode_parameters + offs, src, sizeof(uint64) * (num));
 }
 
+/**
+ * Copy \a num string parameters from the global string parameter array to the \a dst array.
+ * @param dst  Destination array of string parameters.
+ * @param offs Index in the global array to copy the first string parameter from.
+ * @param num  Number of string parameters to copy.
+ */
 static inline void CopyOutDParam(uint64 *dst, int offs, int num)
 {
 	extern uint64 _decode_parameters[20];