diff --git a/README.md b/README.md
index 6f38196..679befd 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,9 @@ A _credentials.json_ file needs to exist in the same directory containing an `"a
 
 ## Updating
 
-The [update](./update) directory contains a simple node program that you run and provide a domain (`update/update.js iojs.org`) which will read the aliases, fetch the list of mail routes from mailgun and update the routes to make sure they match the required aliases.
+The [update](./update) directory contains a simple node program that you run and provide a domain (`update/update.js iojs.org`) which will read the aliases, fetch the list of mail routes from Mailgun and update the routes to make sure they match the required aliases. The Mailgun API key for the given domain is required to make this work.
+
+Members of the Build Working Group "Infra" team (Rod Vagg, Johan Bergström, Michael Dawson and João Reis as of writing) can access the Mailgun API key via the Rackspace API or in the `admin_logins.md` file in the secrets repo (build/infra/). This key must be placed in a file named `iojs.org/credentials.json` in the form: `{ "api-key": "key-abc..." }`.
 
 ## License & copyright