Environment
$ aws --version
aws-cli/2.0.4 Python/3.7.5 Windows/10 botocore/2.0.0dev8
AWS Console
Command:
aws ssm get-parameters-by-path --path "/site/"
Error message:
An error occurred (ValidationException) when calling the GetParametersByPath operation: The parameter doesn't meet the parameter name requirements. The parameter name must begin with a forward slash "/". It can't be prefixed with \"aws\" or \"ssm\" (case-insensitive). It must use only letters, numbers, or the following symbols: . (period), - (hyphen), _ (underscore). Special characters are not allowed. All sub-paths, if specified, must use the forward slash symbol "/". Valid example: /get/parameters2-/by1./path0_.
AWS docs:
https://docs.aws.amazon.com/cli/latest/reference/ssm/get-parameters-by-path.html
UPDATE
The command works in Windows command prompt, this issue is with Git bash for windows.
Try upgrading your AWS cli client. There's a bug that was floating around and your version might be affected.
See Why am I getting an error when querying SSM parameters via get-parameters-by-path?