Yes, it is possible to add MessageAttributes when publishing from AWS EventBridge to SNS as a rule target in order to enable subscription filtering.

Here is an example of creating an SNS topic with a specific set of attributes and then creating an EventBridge rule that publishes to that topic with message attributes:

import boto3

# Create SNS client
sns_client = boto3.client('sns')

# Create SNS topic with specific set of attributes
topic_response = sns_client.create_topic(
    Name='my-topic',
    Attributes={
        'DisplayName': 'My Topic',
        'TopicArn': 'arn:aws:sns:us-east-1:123456789012:my-topic',
        'DeliveryPolicy': {
            'http': {
                'defaultHealthyRetryPolicy': {
                    'minDelayTarget': 1,
                    'maxDelayTarget': 2,
                    'numRetries': 3,
                    'numMaxDelayRetries': 2,
                    'backoffFunction': 'linear'
                },
                'disableSubscriptionOverrides': False,
                'defaultThrottlePolicy': {
                    'maxReceivesPerSecond': 5
                },
                'version': '2012-10-17'
            }
        }
    }
)

# Create EventBridge client
event_bridge_client = boto3.client('events')

# Create EventBridge rule that publishes to SNS topic with message attributes
rule_response = event_bridge_client.put_rule(
    Name='my-rule',
    EventPattern={
        'source': ['my-source']
    },
    State='ENABLED',
    Targets=[
        {
            'Arn': topic_response['TopicArn'],
            'Id': 'my-target',
            'InputPath': '$.detail',
            'InputTransformer': {
                'InputPathsMap': {
                    'attribute1': '$.my_attribute1',
                    'attribute2': '$.my_attribute2'
                },
                'InputTemplate': json.dumps({
                    'Default': '$',
                    'my_message': {
                        'attribute1.$': '$.my_attribute1',
                        'attribute2.$': '$.my_attribute2',
                        'content.$': '$'
                    }
                })
            },