diff --git a/libc/include/stdio_ext.h b/libc/include/stdio_ext.h
index b8aa68d..3aa183d 100644
--- a/libc/include/stdio_ext.h
+++ b/libc/include/stdio_ext.h
@@ -26,32 +26,113 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _STDIO_EXT_H
-#define _STDIO_EXT_H
+#pragma once
+
+/**
+ * @file stdio_ext.h
+ * @brief Extra standard I/O functionality. See also `<stdio.h>`.
+ */
 
 #include <sys/cdefs.h>
 #include <stdio.h>
 
-
 __BEGIN_DECLS
 
+/**
+ * [__fbufsize(3)](http://man7.org/linux/man-pages/man3/__fbufsize.3.html) returns the size of
+ * the stream's buffer.
+ *
+ * Available since API level 23.
+ */
 size_t __fbufsize(FILE* __fp) __INTRODUCED_IN(23);
+
+/**
+ * [__freadable(3)](http://man7.org/linux/man-pages/man3/__freadable.3.html) returns non-zero if
+ * the stream allows reading, 0 otherwise.
+ *
+ * Available since API level 23.
+ */
 int __freadable(FILE* __fp) __INTRODUCED_IN(23);
+
+/**
+ * [__freading(3)](http://man7.org/linux/man-pages/man3/__freading.3.html) returns non-zero if
+ * the stream's last operation was a read, 0 otherwise.
+ *
+ * Available since API level 28.
+ */
 int __freading(FILE* __fp) __INTRODUCED_IN(28);
+
+/**
+ * [__fwritable(3)](http://man7.org/linux/man-pages/man3/__fwritable.3.html) returns non-zero if
+ * the stream allows writing, 0 otherwise.
+ *
+ * Available since API level 23.
+ */
 int __fwritable(FILE* __fp) __INTRODUCED_IN(23);
+
+/**
+ * [__fwriting(3)](http://man7.org/linux/man-pages/man3/__fwriting.3.html) returns non-zero if
+ * the stream's last operation was a write, 0 otherwise.
+ *
+ * Available since API level 28.
+ */
 int __fwriting(FILE* __fp) __INTRODUCED_IN(28);
+
+/**
+ * [__flbf(3)](http://man7.org/linux/man-pages/man3/__flbf.3.html) returns non-zero if
+ * the stream is line-buffered, 0 otherwise.
+ *
+ * Available since API level 23.
+ */
 int __flbf(FILE* __fp) __INTRODUCED_IN(23);
+
+/**
+ * [__fpurge(3)](http://man7.org/linux/man-pages/man3/__fpurge.3.html) discards the contents of
+ * the stream's buffer.
+ *
+ * Available since API level 23.
+ */
 void __fpurge(FILE* __fp) __INTRODUCED_IN(23);
+
+/**
+ * [__fpending(3)](http://man7.org/linux/man-pages/man3/__fpending.3.html) returns the number of
+ * bytes in the output buffer.
+ *
+ * Available since API level 23.
+ */
 size_t __fpending(FILE* __fp) __INTRODUCED_IN(23);
+
+/**
+ * [_flushlbf(3)](http://man7.org/linux/man-pages/man3/_flushlbf.3.html) flushes all
+ * line-buffered streams.
+ *
+ * Available since API level 23.
+ */
 void _flushlbf(void) __INTRODUCED_IN(23);
 
+/**
+ * `__fseterr` sets the
+ * stream's error flag (as tested by ferror() and cleared by fclearerr()).
+ *
+ * Available since API level 28.
+ */
 void __fseterr(FILE* __fp) __INTRODUCED_IN(28);
 
+/** __fsetlocking() constant to query locking type. */
 #define FSETLOCKING_QUERY 0
+/** __fsetlocking() constant to set locking to be maintained by stdio. */
 #define FSETLOCKING_INTERNAL 1
+/** __fsetlocking() constant to set locking to be maintained by the caller. */
 #define FSETLOCKING_BYCALLER 2
+
+/**
+ * [__fsetlocking(3)](http://man7.org/linux/man-pages/man3/__fsetlocking.3.html) sets the
+ * stream's locking mode to one of the `FSETLOCKING_` types.
+ *
+ * Returns the current locking style, `FSETLOCKING_INTERNAL` or `FSETLOCKING_BYCALLER`.
+ *
+ * Available since API level 23.
+ */
 int __fsetlocking(FILE* __fp, int __type) __INTRODUCED_IN(23);
 
 __END_DECLS
-
-#endif /* _STDIO_EXT_H */