Why do I get InvalidDocumentContent when trying to create a SSM document?

I want to run a few shell commands on an EC2 instance, so I came across the AWS Systems Manager Run Command, which uses a SSM document.

I am trying to create a command document, but I get an InvalidDocumentContent error in the step name.

Here is the document:

{
  "schemaVersion": "2.2",
  "description": "Run svc-db-proxy Container",
  "parameters": {
    "AccessKeyID": {
      "type": "String",
      "description": "AWS Access Key ID"
    },
    "SecretAccessKey": {
      "type": "String",
      "description": "AWS Secret Access Key"
    },
    "AWSRegion": {
      "type": "String",
      "description": "AWS Region",
      "default": "ca-central-1"
    },
    "Registry": {
      "type": "String",
      "description": "AWS ECR Registry URL"
    },
    "Repo": {
      "type": "String",
      "description": "AWS ECR Repository"
    },
    "Tag": {
      "type": "String",
      "description": "GitHub SHA used for Image tag"
    }
  },
  "mainSteps": [
    {
      "action": "aws:runShellScript",
      "name": "Deploy svc db proxy container",
      "inputs": {
        "timeoutSeconds": "3600",
        "runCommand": [
          "#!/bin/bash",
          "export AWS_ACCESS_KEY_ID=\"{{AccessKeyID}}\"",
          "export AWS_SECRET_ACCESS_KEY=\"{{SecretAccessKey}}\"",
          "docker login -u AWS -p $(aws ecr get-login-password --region \"{{AWSRegion}}\") {{Registry}}",
          "docker kill {{Repo}} || true",
          "docker container prune -f || true",
          "docker image prune -af || true",
          "docker pull {{Registry}}/{{Repo}}:{{Tag}}",
          "docker run --name {{Repo}} -p 8001:8000 -d {{Registry}}/{{Repo}}:{{Tag}}",
          "docker logout {{Registry}}",
          "unset \"AWS_ACCESS_KEY_ID\"",
          "unset \"AWS_SECRET_ACCESS_KEY\""
        ]
      }
    }
  ]
}

The step name cannot include spaces.

As per the docs, the allowed regular expression pattern for name is [a-zA-Z0-9_]+$. This pattern excludes spaces.

Remove the spaces & it will pass validation e.g.

"name": "deploySvcContainer",