readme: Notes about CLI tools

Author: neilpa

README.md

@@ -12,7 +12,20 @@ TODO
 
 ## Tools
 
-TODO
+There are a few simple CLI tools include for manipulating JPEG/JFIF files that exercise functionality
+exposed by this module.
+
+### jfifcom
+
+Append free-form comment (`COM`) segments to an existing JPEG file.
+
+### jfifstat
+
+Prints segment markers, sizes, and optional `APPN` signatures from a JPEG until the image stream.
+
+### xmpdump
+
+Extracts and prints [XMP](https://www.adobe.com/products/xmp.html) data from `APP1` segments from JPEG file(s).
 
 ## License