The URL Query String Parameters is defined in AWS::Serverless::Function rather than AWS::Serverless::Api using RequestParameters property.
All parameter names must start with method.request and must be limited to method.request.header, method.request.querystring, or method.request.path.
For example to define email, name in URL Query String Parameters and Authorization in HTTP Request Headers u can do the following:
Events:
ApiEvent:
Type: Api
Properties:
Path: /path
Method: get
RequestParameters:
- method.request.querystring.email:
Required: true
Caching: false
- method.request.querystring.name:
Required: true
Caching: false
- method.request.header.Authorization:
Required: true
Caching: true
I hope this helps.