add details about auth system to readme

1 files changed, 25 insertions, 1 deletions

diff --git a/README.md b/README.md
index ab02277..5435278 100644
--- a/README.md
+++ b/README.md
@@ -6,4 +6,28 @@ to facilitate easy use in a dynamic dns kinda situation.
 "it's a thing that tells you your IP"  
 -> "gets your IP?"  
 -> "IPer"  
--> "piper!"
\ No newline at end of file
+-> "piper!"
+
+send an `Authorization` header with your request to track changes in your IP
+address. The value you provide can only contain Base-64 characters, but does
+not have to be valid Base-64.
+
+If a request is received with an `Authorization` header, piper will compare the
+IP the request came from with the last IP to use that `Authorization` value.
+There are three possible situations and two responses:
+
+A `200` status code will be returned, with an IP in the body, if:
+- A request has never been made with the provided auth value
+- The last request to use the auth value came from a different IP address
+
+A `302` status code will be returned, with no body, if:
+- The last request to use the auth value comes from the same IP address
+
+You may specify a `Content-Type` of `application/json` or `text/plain`. Example
+responses are below:
+
+**`application/json`**  
+`{"ip": "127.0.0.1"}`
+
+**`text/plain`**  
+`127.0.0.1`
\ No newline at end of file