# Publish messages to an Amazon SNS topic with Step Functions
<a name="connect-sns"></a>

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
<a name="connect-sns-api"></a>
+ [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
<a name="sns-iam"></a>

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": "*"
        }
    ]
}
```