Cognito user pool authorizer With Serverless Framework

If you want to set the authorizer to a Cognito User Pool you have declared in your resources you must use CloudFormation to create the authorizer as well.

functions:
  functionName:
    # ...
    events:
      - http:
          # ...
          authorizer: 
             type: COGNITO_USER_POOLS
             authorizerId: 
               Ref: ApiGatewayAuthorizer

resources:
  Resources:
    ApiGatewayAuthorizer: 
      Type: AWS::ApiGateway::Authorizer
      Properties: 
        Name: CognitoUserPool
        Type: COGNITO_USER_POOLS
        IdentitySource: method.request.header.Authorization
        RestApiId: 
          Ref: ApiGatewayRestApi
        ProviderARNs: 
          - Fn::GetAtt:
              - UserPool
              - Arn

    UserPool:
      Type: AWS::Cognito::UserPool

Yes . Serverless (v1.5) support to Cognito user pool authorizer.

If you use previous version of serverless you have to update v1.5 or later.

For the user-pool authorization of api end point you have to specify pool arn.

functions:
  hello:
    handler: handler.hello
    events:
      - http:
          path: hello
          method: get
          integration: lambda
          authorizer:
            name: authorizer
            arn: arn:aws:cognito-idp:us-east-1:123456789:userpool/us-east-1_XXXXXX

More details read this article.