# Publish messages to an Amazon SNS topic with Step Functions
Amazon SNS

Learn how to use Step Functions to publish messages to an Amazon SNS topic. This page lists the supported Amazon SNS API actions and provides example `Task` states to publish message to Amazon SNS.

To learn about integrating with AWS services in Step Functions, see [Integrating services](integrate-services.md) and [Passing parameters to a service API in Step Functions](connect-parameters.md).

**Key features of Optimized Amazon SNS integration**  
There are no specific optimizations for the [Request Response](connect-to-resource.md#connect-default) or [Wait for a Callback with Task Token](connect-to-resource.md#connect-wait-token) integration patterns.

The following includes a `Task` state that publishes to an Amazon Simple Notification Service (Amazon SNS) topic.

```
{
 "StartAt": "Publish to SNS",
 "States": {
   "Publish to SNS": {
     "Type": "Task",
     "Resource": "arn:aws:states:::sns:publish",
     "Arguments": {
       "TopicArn": "arn:aws:sns:region:account-id:myTopic",
       "Message": "{% states.input.message %}",
       "MessageAttributes": {
         "my_attribute_no_1": {
           "DataType": "String",
           "StringValue": "value of my_attribute_no_1"
         },
         "my_attribute_no_2": {
           "DataType": "String",
           "StringValue": "value of my_attribute_no_2"
         }
       }
     },
     "End": true
    }
  }
}
```

**Passing dynamic values**. You can modify the above example to dynamically pass an attribute from this JSON payload:

```
{
  "message": "Hello world",
  "SNSDetails": {
    "attribute1": "some value",
    "attribute2": "some other value",
  }
}
```

The following sets values using JSONata expressions for the `StringValue` fields:

```
"MessageAttributes": {
  "my_attribute_no_1": {
      "DataType": "String",
      "StringValue": "{% $states.input.SNSDetails.attribute1 %}"
  },
  "my_attribute_no_2": {
      "DataType": "String",
      "StringValue": "{% $states.input.SNSDetails.attribute2 %}"
  }
```

The following includes a `Task` state that publishes to an Amazon SNS topic, and then waits for the task token to be returned. See [Wait for a Callback with Task Token](connect-to-resource.md#connect-wait-token).

```
{  
   "StartAt":"Send message to SNS",
   "States":{  
      "Send message to SNS":{  
         "Type":"Task",
         "Resource":"arn:aws:states:::sns:publish.waitForTaskToken",
         "Arguments":{  
            "TopicArn":"arn:aws:sns:region:account-id:myTopic",
            "Message":{  
               "Input":"{% states.input.message %}",
               "TaskToken": "{% $states.context.Task.Token %}"
            }
         },
         "End":true
      }
   }
}
```

## Optimized Amazon SNS APIs
Supported APIs
+ [https://docs.aws.amazon.com/sns/latest/api/API_Publish.html](https://docs.aws.amazon.com/sns/latest/api/API_Publish.html)

**Parameters in Step Functions are expressed in PascalCase**  
Even if the native service API is in camelCase, for example the API action `startSyncExecution`, you specify parameters in PascalCase, such as: `StateMachineArn`.

**Quota for input or result data**  
When sending or receiving data between services, the maximum input or result for a task is 256 KiB of data as a UTF-8 encoded string. See [Quotas related to state machine executions](service-quotas.md#service-limits-state-machine-executions).

## IAM policies for calling Amazon SNS
IAM policies

The following example templates show how AWS Step Functions generates IAM policies based on the resources in your state machine definition. For more information, see [How Step Functions generates IAM policies for integrated services](service-integration-iam-templates.md) and [Discover service integration patterns in Step Functions](connect-to-resource.md).

*Static resources*

****  

```
{
    "Version":"2012-10-17",		 	 	 
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "sns:Publish"
            ],
            "Resource": [
                "arn:aws:sns:us-east-1:123456789012:myTopicName"
            ]
        }
    ]
}
```

*Resources based on a Path, or publishing to `TargetArn` or `PhoneNumber`*

****  

```
{
    "Version":"2012-10-17",		 	 	 
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "sns:Publish"
            ],
            "Resource": "*"
        }
    ]
}
```