diff --git a/README.md b/README.md
index 77b9f14..4496b7b 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,11 @@ The S3 compatible endpoint needs to be configured in the `s3` object of the conf
 - `secure` - specifies if __*https*__ protocol is used.
 - `host` - is the \<hostname>\[:\<port>] for the S3 compatible endpoint.
 
+Additionally the following environment variables need to be populated to interact with the S3 endpoint.
+
+- `ACM_S3_ACCESS` - A valid S3 Access Key for the endpoint.
+- `ACM_S3_SECRET` - A valid S3 Secret Key for the Access Key on the endpoint.
+
 ### Common Options
 
 - `-c, --config`: The config file to read. Default file is `acm-config.json` in the current directory.