Say which API level fdsan/fdtrack appeared at.

Test: N/A
Change-Id: Id29db9a5ec6a039af95ce3cdd421542ac862f339
diff --git a/docs/fdsan.md b/docs/fdsan.md
index 0e6783d..e0cf80a 100644
--- a/docs/fdsan.md
+++ b/docs/fdsan.md
@@ -2,6 +2,8 @@
 
 [TOC]
 
+fdsan is a file descriptor sanitizer added to Android in API level 29.
+
 ### Background
 *What problem is fdsan trying to solve? Why should I care?*
 
diff --git a/docs/fdtrack.md b/docs/fdtrack.md
index 5bc9860..7cf6e1f 100644
--- a/docs/fdtrack.md
+++ b/docs/fdtrack.md
@@ -1,5 +1,9 @@
 ## fdtrack
 
+[TOC]
+
+fdtrack is a file descriptor leak checker added to Android in API level 30.
+
 fdtrack consists of two parts: a set of hooks in bionic to register a callback
 that's invoked on file descriptor operations, and a library that implements a
 hook to perform and store backtraces for file descriptor creation.