diff --git a/signing_method.go b/signing_method.go
index 109dd0f..12cf0f3 100644
--- a/signing_method.go
+++ b/signing_method.go
@@ -2,11 +2,11 @@ package jwt
 
 var signingMethods = map[string]func() SigningMethod{}
 
-// Signing method
+// Implement SigningMethod to add new methods for signing or verifying tokens.
 type SigningMethod interface {
-	Verify(signingString, signature string, key interface{}) error
-	Sign(signingString string, key interface{}) (string, error)
-	Alg() string
+	Verify(signingString, signature string, key interface{}) error // Returns nil if signature is valid
+	Sign(signingString string, key interface{}) (string, error)    // Returns encoded signature or error
+	Alg() string                                                   // returns the alg identifier for this method (example: 'HS256')
 }
 
 // Register the "alg" name and a factory function for signing method.