diff --git a/tools/build/options/WITH_ASAN b/tools/build/options/WITH_ASAN
new file mode 100644
--- /dev/null
+++ b/tools/build/options/WITH_ASAN
@@ -0,0 +1,4 @@
+Build the base system with Address Sanitizer (ASan) to detect
+memory corruption bugs such as buffer overflows or use-after-free.
+Requires that Clang be used as the base system compiler
+and that the runtime support library is available.
diff --git a/tools/build/options/WITH_UBSAN b/tools/build/options/WITH_UBSAN
new file mode 100644
--- /dev/null
+++ b/tools/build/options/WITH_UBSAN
@@ -0,0 +1,4 @@
+Build the base system with Undefined Behavior Sanitizer (UBSan) to detect
+various kinds of undefined behavior at runtime.
+Requires that Clang be used as the base system compiler
+and that the runtime support library is available