Resources: BadDefinitionUriApi: Type: AWS::Serverless::Api Properties: StageName: Prod DefinitionUri: http://sam-demo-bucket/webpage_swagger.json BadDefinitionUriTypeApi: Type: AWS::Serverless::Api Properties: StageName: Prod DefinitionUri: Bucket: somebucket # Key property is missing BadCodeUriFunction: Type: AWS::Serverless::Function Properties: CodeUri: http://dropbox.com/my-object.zip Runtime: python2.7 Handler: hello.handler BadCodeUriTypeFunction: Type: AWS::Serverless::Function Properties: CodeUri: Key: somebucket # Buckiet property is missing Runtime: python2.7 Handler: hello.handler ExternalS3Function: Type: AWS::Serverless::Function Properties: CodeUri: s3://sam-demo-bucket/notifications.zip Handler: index.save_notification Runtime: nodejs12.x Events: S3Event: Type: S3 Properties: Bucket: mybucket Events: s3:ObjectCreated:*