YAML script to tag stopped EC2 instances using automation document in Systems Manager

I am trying to create an automation document in AWS for a maintenance task- which will add a tag to all the stopped EC2 instances in a region.

This is the yaml I'm working with:

schemaVersion: '0.3'
description: Automation to add tags to stopped instances.

parameters:
  - name: Region
    type: String
    description: The AWS region to run the automation in.
    default: us-east-1

  - name: TagKey
    type: String
    description: The key of the tag to be added to the instances.
    default: Status

  - name: TagValue
    type: String
    description: The value of the tag to be added to the instances.
    default: Stopped

mainSteps:
  - action: 'aws:runCommand'
    name: 'FindStoppedInstances'
    inputs:
      DocumentName: 'AWS-RunShellScript'
      Parameters:
        commands:
          - |
            # Get the list of stopped EC2 instance IDs
            instance_ids=$(aws ec2 describe-instances \
              --filters "Name=instance-state-name,Values=stopped" \
              --query "Reservations[*].Instances[*].InstanceId" \
              --output text)
            
            echo "$instance_ids"
        executionTimeout: ['3600']
    outputs:
      - Name: 'instance_ids'
        Selector: '$.Payload'
        Type: 'StringList'

  - action: 'aws:runCommand'
    name: 'TagStoppedInstances'
    inputs:
      DocumentName: 'AWS-RunShellScript'
      Parameters:
        commands:
          - |
            # Loop through each stopped instance and tag it
            for instance_id in {{ instance_ids }}; do
              echo "Adding tag to instance $instance_id"
              aws ec2 create-tags --resources $instance_id --tags Key={{ TagKey }},Value={{ TagValue }}
            done
        executionTimeout: ['3600']

frankly, I have not used YAML before and took help from chatgpt. I don't want to use lambda for this task. This document is giving an error - (parameters) Parameter definition does not match any following types, String, StringList, Boolean, Integer, StringMap, MapList, AWS::EC2::Instance::Id, AWS::IAM::Role::Arn, AWS::S3::Bucket::Name, List<AWS::EC2::Instance::Id>, List<AWS::IAM::Role::Arn>, List<AWS::S3::Bucket::Name>

Can someone please help me on how to correct this script? After putting the tags, I want to start those EC2s. Once my patching task is complete (for which I am using run command), I want to shut down the EC2s which have this tag again and remove this tag.

There are couple of issues with the script. Update the parameter section to have keys not list:

parameters:
  Region:
    type: String
    description: The AWS region to run the automation in.
    default: us-east-1

  TagKey:
    type: String
    description: The key of the tag to be added to the instances.
    default: Status

  TagValue:
    type: String
    description: The value of the tag to be added to the instances.
    default: Stopped

Then update the script in action TagStoppedInstances to reference the previous action:

  - action: 'aws:runCommand'
    name: 'TagStoppedInstances'
    inputs:
      DocumentName: 'AWS-RunShellScript'
      Parameters:
        commands:
          - |
            # Loop through each stopped instance and tag it
            for instance_id in {{ FindStoppedInstances.instance_ids }}; do
              echo "Adding tag to instance $instance_id"
              aws ec2 create-tags --resources $instance_id --tags Key={{ TagKey }},Value={{ TagValue }}
            done
        executionTimeout: ['3600']

Instead of running scripts that call AWS CLI I would suggest using actions that run AWS API. A sample of similar workflow can be found on AWS Systems Manager User Guide