diff --git a/src/gamelog_internal.h b/src/gamelog_internal.h
index 755e995e40..914f71389e 100644
--- a/src/gamelog_internal.h
+++ b/src/gamelog_internal.h
@@ -32,6 +32,13 @@ using GrfIDMapping = std::map<uint32_t, GRFPresence>;
 struct LoggedChange {
 	LoggedChange(GamelogChangeType type = GLCT_NONE) : ct(type) {}
 	virtual ~LoggedChange() = default;
+
+	/**
+	 * Format the content of this change into the given output.
+	 * @param output_iterator Destination of the formatted content.
+	 * @param grf_names Cache/mapping of names of NewGRFs seen in the logs.
+	 * @param action_type The context in which this method was called.
+	 */
 	virtual void FormatTo(std::back_insert_iterator<std::string> &output_iterator, GrfIDMapping &grf_names, GamelogActionType action_type) = 0;
 
 	GamelogChangeType ct{};
diff --git a/src/newgrf/newgrf_act3.cpp b/src/newgrf/newgrf_act3.cpp
index 0ca425dc2f..6b7eae7104 100644
--- a/src/newgrf/newgrf_act3.cpp
+++ b/src/newgrf/newgrf_act3.cpp
@@ -153,10 +153,23 @@ static void VehicleMapSpriteGroup(ByteReader &buf, GrfSpecFeature feature, uint8
 	}
 }
 
-/** Handler interface for mapping sprite groups. */
+/** Handler interface for mapping sprite groups to their respective feature specific specifications. */
 struct MapSpriteGroupHandler {
 	virtual ~MapSpriteGroupHandler() = default;
+
+	/**
+	 * Map a SpriteGroup to specific 'cargo type' of a specification.
+	 * @param local_id The NewGRF-local id to map to.
+	 * @param cid The 'cargo type' to map for.
+	 * @param group The SpriteGroup to link to the specification.
+	 */
 	virtual void MapSpecific(uint16_t local_id, uint8_t cid, const SpriteGroup *group) = 0;
+
+	/**
+	 * Map default/fallback SpriteGroup to a specification.
+	 * @param local_id The NewGRF-local id to map to.
+	 * @param group The SpriteGroup to link to the specification.
+	 */
 	virtual void MapDefault(uint16_t local_id, const SpriteGroup *group) = 0;
 };
 
diff --git a/src/newgrf_commons.h b/src/newgrf_commons.h
index 134f469d6e..7b2714c096 100644
--- a/src/newgrf_commons.h
+++ b/src/newgrf_commons.h
@@ -201,6 +201,11 @@ protected:
 	uint16_t max_entities; ///< what is the amount of entities, old and new summed
 
 	uint16_t invalid_id;   ///< ID used to detected invalid entities
+	/**
+	 * Checks whether the given ID is valid in the context of this override manager.
+	 * @param testid The ID to test.
+	 * @return Whether the ID is valid.
+	 */
 	virtual bool CheckValidNewID([[maybe_unused]] uint16_t testid) { return true; }
 
 public:
diff --git a/src/newgrf_spritegroup.cpp b/src/newgrf_spritegroup.cpp
index a5c5d07408..57216f1169 100644
--- a/src/newgrf_spritegroup.cpp
+++ b/src/newgrf_spritegroup.cpp
@@ -110,8 +110,10 @@ static inline uint32_t GetVariable(const ResolverObject &object, ScopeResolver *
 
 /**
  * Store a value into the persistent storage area (PSA). Default implementation does nothing (for newgrf classes without storage).
+ * @param pos The position into the storage area.
+ * @param value The new value to store.
  */
-/* virtual */ void ScopeResolver::StorePSA(uint, int32_t) {}
+/* virtual */ void ScopeResolver::StorePSA([[maybe_unused]] uint pos, [[maybe_unused]] int32_t value) {}
 
 /**
  * Get the real sprites of the grf.
@@ -128,9 +130,11 @@ static inline uint32_t GetVariable(const ResolverObject &object, ScopeResolver *
 
 /**
  * Get a resolver for the \a scope.
+ * @param scope The scope to resolve.
+ * @param relative The relative in case of a #VSG_SCOPE_RELATIVE.
  * @return The resolver for the requested scope.
  */
-/* virtual */ ScopeResolver *ResolverObject::GetScope(VarSpriteGroupScope, uint8_t)
+/* virtual */ ScopeResolver *ResolverObject::GetScope([[maybe_unused]] VarSpriteGroupScope scope, [[maybe_unused]] uint8_t relative)
 {
 	return &this->default_scope;
 }
diff --git a/src/newgrf_spritegroup.h b/src/newgrf_spritegroup.h
index 95486aa78f..37a8f7303b 100644
--- a/src/newgrf_spritegroup.h
+++ b/src/newgrf_spritegroup.h
@@ -47,7 +47,11 @@ extern SpriteGroupPool _spritegroup_pool;
 struct SpriteGroup : SpriteGroupPool::PoolItem<&_spritegroup_pool> {
 protected:
 	SpriteGroup(SpriteGroupID index) : SpriteGroupPool::PoolItem<&_spritegroup_pool>(index) {}
-	/** Base sprite group resolver */
+	/**
+	 * Resolves a callback or rerandomisation callback to a NewGRF.
+	 * @param object Information needed to resolve the group.
+	 * @return The result of resolving this SpriteGroup.
+	 */
 	virtual ResolverResult Resolve(ResolverObject &object) const = 0;
 
 public:
diff --git a/src/script/api/script_object.hpp b/src/script/api/script_object.hpp
index 76e7d3993c..fc8558ca2e 100644
--- a/src/script/api/script_object.hpp
+++ b/src/script/api/script_object.hpp
@@ -46,8 +46,11 @@ public:
 	SimpleCountedObject() : ref_count(0) {}
 	virtual ~SimpleCountedObject() = default;
 
+	/** Increase the reference count by one. */
 	inline void AddRef() { ++this->ref_count; }
+	/** Decrease the reference count by one. Once zero call FinaleRelease and then destruct the object. */
 	void Release();
+	/** Called during Release, so the object can throw exceptions (you cannot in destructors). */
 	virtual void FinalRelease() {};
 
 private:
diff --git a/src/window.cpp b/src/window.cpp
index 81a8b95f56..3867676bb9 100644
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -1101,6 +1101,7 @@ void Window::CloseChildWindowById(WindowClass wc, WindowNumber number) const
 
 /**
  * Hide the window and all its child windows, and mark them for a later deletion.
+ * @param data Window specific data to be passed through the window close functions.
  */
 void Window::Close([[maybe_unused]] int data)
 {