diff --git a/README.md b/README.md
index 36cf579..f7a24b5 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,13 @@
 # too-soon
 
-alert on upcoming expirations
\ No newline at end of file
+alert on upcoming expirations.
+like, certificates for my domain expire too soon.
+
+Default is expiration within 20 days.
+
+## inital functionality
+
+Arguments passed to the tool are PEM encoded x509 files.
+No output at all if all good.
+If any of the PEM x509 files have DNS Names _and_ the notAfter date is within 20day from today, then output text alert to stdout and return non-zero exit code.
+