diff --git a/README.md b/README.md
index aa4623f..5dd9999 100644
--- a/README.md
+++ b/README.md
@@ -49,8 +49,8 @@ jobs:
 ### Parameters
 
 #### When using official Swift releases:
-  - `branch`: the Swift "version" to be installed. This may be either a pre-release branch (e.g. `swift-5.5-branch`), a release branch (e.g. `swift-5.5-release`) or the development branch (`swift-development`).
-  - `tag`: the actual build tag to install. This may be either a release snapshot tag (e.g. `5.5-DEVELOPMENT-SNAPSHOT-2021-09-18-a`), development snapshot tag  (e.g. `DEVELOPMENT-SNAPSHOT-2021-09-28-a`), or a release tag (e.g. `5.5-RELEASE`).
+  - `branch`: (**Note:** this is not a git branch name) the Swift "version" to be installed. This may be either a pre-release branch (e.g. `swift-5.5-branch`), a release branch (e.g. `swift-5.5-release`) or the development branch (`swift-development`).
+  - `tag`: (**Note:** this is not a git tag name) the actual build tag to install, minus the “`swift-`” prefix. May indicate a release snapshot (e.g. `5.5-DEVELOPMENT-SNAPSHOT-2021-09-18-a`), development snapshot  (e.g. `DEVELOPMENT-SNAPSHOT-2021-09-28-a`), or a release (e.g. `5.5-RELEASE`).
 
 #### When using Swift builds from a Github repository release:
 - `github-repo`: Github repo in "owner/repo" format