diff --git a/wfassoc-cdylib/codegen/wfassoc.h b/wfassoc-cdylib/codegen/wfassoc.h
index 3c99452..816739b 100644
--- a/wfassoc-cdylib/codegen/wfassoc.h
+++ b/wfassoc-cdylib/codegen/wfassoc.h
@@ -1,3 +1,12 @@
+/**
+ * @file wfassoc.h
+ * @brief Windows File Association C API header
+ *
+ * This header provides a C-compatible API for managing Windows file associations,
+ * including schema creation, program registration, and extension management.
+ * The API is designed to work with both C and C++ compilers.
+ */
+
 #pragma once
 #ifndef __WFASSOC_H__
 #define __WFASSOC_H__
@@ -13,8 +22,25 @@
 
 
 #ifdef __cplusplus
+namespace wfassoc {
+#endif // __cplusplus
+
+
+#ifdef __cplusplus
+/** Type representing a null-terminated UTF-8 C-style string */
 using CStyleString = const char*;
+/** 
+ * @brief Type representing a handle/token for managed objects 
+ * 
+ * This library use object pool to manage any objects created during calling.
+ * And we expose this type as an opaque handle for visiting your created object.
+ */
 using Token = uint64_t;
+/** 
+ * @brief Type representing an icon handle (opaque pointer)
+ * 
+ * This type is equivalent with Win32 HICON type.
+ */
 using HICON = void*;
 #else  // __cplusplus
 typedef const char *CStyleString;
@@ -24,7 +50,9 @@ typedef void *HICON;
 
 
 #ifdef __cplusplus
+/** Invalid icon handle value */
 constexpr HICON INVALID_HICON = nullptr;
+/** Invalid index value used for error conditions */
 constexpr size_t INVALID_INDEX = static_cast<size_t>(-1);
 #else  // __cplusplus
 static const HICON INVALID_HICON = NULL;
@@ -33,113 +61,479 @@ static const size_t INVALID_INDEX = ((size_t)-1);
 
 
 #ifdef __cplusplus
+/**
+ * @brief Registration scope for file associations
+ *
+ * Determines whether a program is registered for the current user or system-wide.
+ */
 enum class Scope : uint32_t {
+    /** Current user scope */
     User = 0u,
+    /** System-wide scope */
     System = 1u
 };
+/**
+ * @brief View mode for querying file association status
+ *
+ * Determines how the association status is viewed/queried.
+ */
 enum class View : uint32_t {
+    /** User-level view */
     User = 0u,
+    /** System-level view */
     System = 1u,
+    /** Combined hybrid view of both user and system */
     Hybrid = 2u
 };
 #else  // __cplusplus
 typedef uint32_t Scope;
+/** Current user scope */
 static const Scope SCOPE_USER = 0u;
+/** System-wide scope */
 static const Scope SCOPE_SYSTEM = 1u;
 typedef uint32_t View;
+/** User-level view */
 static const View VIEW_USER = 0u;
+/** System-level view */
 static const View VIEW_SYSTEM = 1u;
+/** Combined hybrid view of both user and system */
 static const View VIEW_HYBRID = 2u;
 #endif  // __cplusplus
 
 
 #ifdef __cplusplus
-namespace wfassoc {
 extern "C" {
 #endif // __cplusplus
 
+/**
+ * @brief Initialize the wfassoc library
+ *
+ * This function must be called before using the MOST of any other wfassoc functions.
+ * 
+ * @return true on success, false on failure.
+ */
 bool WFStartup(void);
 
+/**
+ * @brief Shutdown the wfassoc library
+ *
+ * Cleans up all allocated resources and object pools.
+ * Should be called when done using the library.
+ *
+ * @return true on success, false on failure.
+ */
 bool WFShutdown(void);
 
+/**
+ * @brief Get the last error message
+ *
+ * Returns a human-readable error message describing the last error that occurred.
+ * The returned error message string is valid until the next API call.
+ * 
+ * For most functions located in this library, except some special function indicated in their notes,
+ * they return boolean value indicating whether function is successful or not.
+ * Once they fail, you can call this function to get a human-readable error message.
+ * 
+ * The execution of this function do not need to be wrapped by WFStartup() and WFShutdown().
+ *
+ * @return Null-terminated UTF-8 string containing the error message.
+ * If no error has occurred, the string is empty.
+ * There is no possibility of a NULL return value.
+ */
 CStyleString WFGetLastError(void);
 
+/**
+ * @brief Check if the current process has administrative privileges
+ *
+ * This function will not throw any error.
+ * There is no necessity to call WFGetLastError() after this function.
+ * The return value only indicates whether the current process has administrative privileges or not.
+ * 
+ * The execution of this function do not need to be wrapped by WFStartup() and WFShutdown().
+ *
+ * @return true if running with admin privileges, false otherwise
+ */
 bool WFHasPrivilege(void);
 
+/**
+ * @brief Get an invalid token value
+ *
+ * In theory, invalid token value should be a constant value.
+ * However, due to the library I used in Rust side, this value only can be fetched at runtime.
+ * So I expose this function to make programmer can fetch this constant value.
+ * Theoretically, you just need to fetch this function only once at the beginning of your program.
+ * 
+ * The execution of this function do not need to be wrapped by WFStartup() and WFShutdown().
+ *
+ * @return An invalid token value
+ */
 Token WFInvalidToken(void);
 
+/**
+ * @brief Create a new Schema object
+ *
+ * A Schema is a sketchpad of a complete program.
+ * For the user of this library, they should create a Schema object first.
+ * Then convert it to a Program object for following operations.
+ *
+ * @param[out] out_schema Pointer to receive the Schema token.
+ * The receiver take the ownership of this Schema object.
+ * And it should be freed by calling WFSchemaDestroy() when it is no longer needed,
+ * or consumed by creating a Program object via WFProgramCreate().
+ * @return true on success, false on failure
+ */
 bool WFSchemaCreate(Token *out_schema);
 
+/**
+ * @brief Destroy a Schema object
+ *
+ * Releases resources associated with the Schema object.
+ *
+ * Usually you do not need to call this function,
+ * because the convertion function from Schema to Program will consume given Schema object to produce Program object.
+ *
+ * @param[in] in_schema Schema token to destroy
+ * @return true on success, false on failure
+ */
 bool WFSchemaDestroy(Token in_schema);
 
+/**
+ * @brief Set the program identifier for a Schema
+ *
+ * @param[in] in_schema Schema token
+ * @param[in] in_value Null-terminated UTF-8 string containing the identifier.
+ * This identifier should not be empty, must start with alphabet character,
+ * and follow with alphabet characters, digits, underline, or hyphens.
+ * @return true on success, false on failure
+ */
 bool WFSchemaSetIdentifier(Token in_schema, CStyleString in_value);
 
+/**
+ * @brief Set the program path for a Schema
+ *
+ * @param[in] in_schema Schema token
+ * @param[in] in_value Null-terminated UTF-8 string containing the program path.
+ * This path should be the fully qualified path to the application.
+ * @return true on success, false on failure
+ */
 bool WFSchemaSetPath(Token in_schema, CStyleString in_value);
 
+/**
+ * @brief Set the program CLSID for a Schema
+ *
+ * @param[in] in_schema Schema token
+ * @param[in] in_value Null-terminated UTF-8 string containing the CLSID.
+ * This CLSID string should be in the format of @c {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} .
+ * Please note that curly braces are required.
+ * @return true on success, false on failure
+ */
 bool WFSchemaSetClsid(Token in_schema, CStyleString in_value);
 
+/**
+ * @brief Set the program name for a Schema (optional)
+ *
+ * @param[in] in_schema Schema token
+ * @param[in] in_value Null-terminated UTF-8 string containing the name, or NULL to clear
+ * @return true on success, false on failure
+ */
 bool WFSchemaSetName(Token in_schema, CStyleString in_value);
 
+/**
+ * @brief Set the program icon for a Schema (optional)
+ *
+ * @param[in] in_schema Schema token
+ * @param[in] in_value Null-terminated UTF-8 string containing the icon path, or NULL to clear
+ * @return true on success, false on failure
+ */
 bool WFSchemaSetIcon(Token in_schema, CStyleString in_value);
 
+/**
+ * @brief Set the program behavior for a Schema (optional)
+ *
+ * @param[in] in_schema Schema token
+ * @param[in] in_value Null-terminated UTF-8 string containing the behavior command, or NULL to clear
+ * @return true on success, false on failure
+ */
 bool WFSchemaSetBehavior(Token in_schema, CStyleString in_value);
 
+/**
+ * @brief Add a string resource entry to a Schema
+ *
+ * @param[in] in_schema Schema token
+ * @param[in] in_name Null-terminated UTF-8 string containing the name of this entry
+ * @param[in] in_value Null-terminated UTF-8 string containing the value of this entry.
+ * It can be a plain string or a reference string to resource.
+ * @return true on success, false on failure
+ */
 bool WFSchemaAddStr(Token in_schema, CStyleString in_name, CStyleString in_value);
 
+/**
+ * @brief Add an icon registry entry to a Schema
+ *
+ * @param[in] in_schema Schema token
+ * @param[in] in_name Null-terminated UTF-8 string containing the name of this entry
+ * @param[in] in_value Null-terminated UTF-8 string containing the value of this entry.
+ * It can be a path to icon or a reference string to resource.
+ * @return true on success, false on failure
+ */
 bool WFSchemaAddIcon(Token in_schema, CStyleString in_name, CStyleString in_value);
 
+/**
+ * @brief Add a behavior registry entry to a Schema
+ *
+ * @param[in] in_schema Schema token
+ * @param[in] in_name Null-terminated UTF-8 string containing the name of this entry
+ * @param[in] in_value Null-terminated UTF-8 string containing the value of this entry.
+ * It should be a valid command line string which use \c %1, \c %2, etc. to represent parameters.
+ * @return true on success, false on failure
+ */
 bool WFSchemaAddBehavior(Token in_schema, CStyleString in_name, CStyleString in_value);
 
+/**
+ * @brief Add a file extension to a Schema
+ *
+ * @param[in] in_schema Schema token
+ * @param[in] in_ext Null-terminated UTF-8 string containing the file extension name (without leading dot).
+ * @param[in] in_ext_name Null-terminated UTF-8 string containing the name pointing to associated name for this extension.
+ * This name should be registered by calling WFSchemaAddStr().
+ * @param[in] in_ext_icon Null-terminated UTF-8 string containing the name pointing to associated icon for this extension.
+ * This name should be registered by calling WFSchemaAddIcon().
+ * @param[in] in_ext_behavior Null-terminated UTF-8 string containing the name pointing to associated behavior for this extension.
+ * This name should be registered by calling WFSchemaAddBehavior().
+ * @return true on success, false on failure
+ */
 bool WFSchemaAddExt(Token in_schema,
                     CStyleString in_ext,
                     CStyleString in_ext_name,
                     CStyleString in_ext_icon,
                     CStyleString in_ext_behavior);
 
+/**
+ * @brief Create a Program object from a Schema
+ *
+ * Please note that this function will consume the Schema object.
+ * It means that the Schema object cannot be used after this call.
+ * And you do not need to call WFSchemaDestroy() for this Schema object after this call.
+ *
+ * @param[in] in_schema Schema token (will be consumed)
+ * @param[out] out_program Pointer to receive the Program token.
+ * The receiver take the ownership of this Program object.
+ * And it should be freed by calling WFProgramDestroy() when it is no longer needed.
+ * @return true on success, false on failure
+ */
 bool WFProgramCreate(Token in_schema, Token *out_program);
 
+/**
+ * @brief Destroy a Program object
+ *
+ * Releases resources associated with the Program.
+ *
+ * @param[in] in_program Program token to destroy
+ * @return true on success, false on failure
+ */
 bool WFProgramDestroy(Token in_program);
 
+/**
+ * @brief Resolve the provided program name of this Program
+ *
+ * @param[in] in_program Program token
+ * @param[out] out_name Pointer to receive the resolved name, or NULL if not found.
+ * This string will be freed at the next API call. Please make a copy immediately if you need to use it longer.
+ * @return true on success, false on failure
+ */
 bool WFProgramResolveName(Token in_program, CStyleString *out_name);
 
+/**
+ * @brief Resolve the Program icon resource
+ *
+ * @param[in] in_program Program token
+ * @param[out] out_icon_rc Pointer to receive the icon resource token, or invalid token if not found.
+ * The caller take the ownership of created icon resource object.
+ * And it should be freed by calling WFIconRcDestroy() when it is no longer needed.
+ * @return true on success, false on failure
+ */
 bool WFProgramResolveIcon(Token in_program, Token *out_icon_rc);
 
+/**
+ * @brief Get the number of file extensions in the Program
+ *
+ * @param[in] in_program Program token
+ * @param[out] out_len Pointer to receive the number of extensions
+ * @return true on success, false on failure
+ */
 bool WFProgramExtsLen(Token in_program, size_t *out_len);
 
+/**
+ * @brief Get a file extension by index
+ *
+ * @param[in] in_program Program token
+ * @param[in] in_index Index of the extension to retrieve
+ * @param[out] out_ext Pointer to receive the file extension token.
+ * The caller take the ownership of created file extension object.
+ * And it should be freed by calling WFExtDestroy() when it is no longer needed.
+ * @return true on success, false on failure
+ */
 bool WFProgramGetExt(Token in_program, size_t in_index, Token *out_ext);
 
+/**
+ * @brief Find a file extension by its body (extension string)
+ *
+ * @param[in] in_program Program token
+ * @param[in] in_body Null-terminated UTF-8 string containing the file extension name (without leading dot) to find.
+ * @param[out] out_index Pointer to receive the file extension index, or INVALID_INDEX if not found.
+ * @return true on success, false on failure
+ */
 bool WFProgramFindExt(Token in_program, CStyleString in_body, size_t *out_index);
 
+/**
+ * @brief Register the Program in the specified scope
+ *
+ * @param[in] in_program Program token
+ * @param[in] in_scope Registration scope
+ * @return true on success, false on failure
+ */
 bool WFProgramRegister(Token in_program, Scope in_scope);
 
+/**
+ * @brief Unregister the Program from the specified scope
+ *
+ * @param[in] in_program Program token
+ * @param[in] in_scope Registration scope
+ * @return true on success, false on failure
+ */
 bool WFProgramUnregister(Token in_program, Scope in_scope);
 
+/**
+ * @brief Check if the Program is registered in the specified scope
+ *
+ * @param[in] in_program Program token
+ * @param[in] in_scope Registration scope for checking
+ * @param[out] out_is_registered Pointer to receive the registration status.
+ * True if the Program is registered in the specified scope, false otherwise.
+ * @return true on success, false on failure
+ */
 bool WFProgramIsRegistered(Token in_program, Scope in_scope, bool *out_is_registered);
 
+/**
+ * @brief Link a file extension in the specified scope
+ *
+ * @param[in] in_program Program token
+ * @param[in] in_scope Registration scope
+ * @param[in] in_index Index of the extension to link
+ * @return true on success, false on failure
+ */
 bool WFProgramLinkExt(Token in_program, Scope in_scope, size_t in_index);
 
+/**
+ * @brief Unlink a file extension in the specified scope
+ *
+ * @param[in] in_program Program token
+ * @param[in] in_scope Registration scope
+ * @param[in] in_index Index of the extension to unlink
+ * @return true on success, false on failure
+ */
 bool WFProgramUnlinkExt(Token in_program, Scope in_scope, size_t in_index);
 
+/**
+ * @brief Query the status of a file extension
+ *
+ * @param[in] in_program Program token
+ * @param[in] in_view View viewpoint.
+ * @param[in] in_index Index of the extension to query
+ * @param[out] out_ext_status Pointer to receive the extension status token, or invalid token if not found.
+ * If the extension is not found, it usually means that this extension is not registered in the specified scope.
+ * The caller take the ownership of created extension status object.
+ * And it should be freed by calling WFExtStatusDestroy() when it is no longer needed.
+ * @return true on success, false on failure
+ */
 bool WFProgramQueryExt(Token in_program, View in_view, size_t in_index, Token *out_ext_status);
 
+/**
+ * @brief Destroy an extension status object
+ *
+ * @param[in] in_ext_status Extension status token to destroy
+ * @return true on success, false on failure
+ */
 bool WFExtStatusDestroy(Token in_ext_status);
 
+/**
+ * @brief Get the name from an extension status object
+ *
+ * @param[in] in_ext_status Extension status token
+ * @param[out] out_name Pointer to receive the name.
+ * There is no possibility that this value is NULL.
+ * We will try to use localized name first, then use raw ProgId name if localized name is not available.
+ * This string will be freed at the next API call. Please make a copy immediately if you need to use it longer.
+ * @return true on success, false on failure
+ */
 bool WFExtStatusGetName(Token in_ext_status, CStyleString *out_name);
 
+/**
+ * @brief Get the icon from an extension status object
+ *
+ * @param[in] in_ext_status Extension status token
+ * @param[out] out_icon Pointer to receive the icon handle, or INVALID_HICON if not available.
+ * This icon handle will be freed once this icon resource object is destroyed.
+ * Please make a copy immediately if you need to use it longer.
+ * @return true on success, false on failure
+ */
 bool WFExtStatusGetIcon(Token in_ext_status, HICON *out_icon);
 
+/**
+ * @brief Destroy an icon resource object
+ *
+ * @param[in] in_icon_rc Icon resource token to destroy
+ * @return true on success, false on failure
+ */
 bool WFIconRcDestroy(Token in_icon_rc);
 
+/**
+ * @brief Get the icon handle from an icon resource object
+ *
+ * @param[in] in_icon_rc Icon resource token
+ * @param[out] out_icon Pointer to receive the icon handle.
+ * There is no possibility that this value is INVALID_HICON.
+ * This icon handle will be freed once this icon resource object is destroyed.
+ * Please make a copy immediately if you need to use it longer.
+ * @return true on success, false on failure
+ */
 bool WFIconRcGetIcon(Token in_icon_rc, HICON *out_icon);
 
+/**
+ * @brief Destroy a file extension object
+ *
+ * @param[in] in_ext Extension token to destroy
+ * @return true on success, false on failure
+ */
 bool WFExtDestroy(Token in_ext);
 
+/**
+ * @brief Get the inner extension string without dot
+ *
+ * @param[in] in_ext Extension token
+ * @param[out] out_inner Pointer to receive the file extension name (without leading dot).
+ * There is no possibility that this value is NULL.
+ * This string will be freed at the next API call. Please make a copy immediately if you need to use it longer.
+ * @return true on success, false on failure
+ */
 bool WFExtGetInner(Token in_ext, CStyleString *out_inner);
 
+/**
+ * @brief Get the inner extension string with dot prefix
+ *
+ * @param[in] in_ext Extension token
+ * @param[out] out_inner Pointer to receive the file extension string (with leading dot).
+ * There is no possibility that this value is NULL.
+ * This string will be freed at the next API call. Please make a copy immediately if you need to use it longer.
+ * @return true on success, false on failure
+ */
 bool WFExtGetDottedInner(Token in_ext, CStyleString *out_inner);
 
 #ifdef __cplusplus
 }  // extern "C"
+#endif  // __cplusplus
+
+#ifdef __cplusplus
 }  // namespace wfassoc
 #endif  // __cplusplus