I'm trying to feed JSON as a String to CloudFormation, and it's not working.

I'm trying to schedule an ECS task using a Scheduler::Schedule CFN resource. Everything works fine until I try to encode the "Input" parameter. "Input" expects a String but ECS needs it to be a JSON object and for the life of me I can't make CFN happy.

For example, assuming my JSON object is:

{"containerOverrides":[{"name":"myapp","command":["mycommand"]}]}

I've tried encoding the JSON object using stringify:

"{\"containerOverrides\":[{\"name\":\"myapp\",\"command\":[\"mycommand\"]}]}"

but CFN responds with "Invalid request provided: JSON syntax error in input for the target: [Source: (String)"

I've also tried HTML encoding:

"{"containerOverrides":[{"name":"myapp","command":["mycommand"]}]}"

but I get the same response from CFN.

If I manually update the Schedule using the AWS Console and then export the Schedule using the CLI I can see the plain JSON in the output. So, the Scheduler service is working with JSON but CFN won't process it properly.