Request Syntax URI Request Parameters Request Body Response Syntax Response Elements Errors See Also

CountTokens

Returns the token count for a given inference request. This operation helps you estimate token usage before sending requests to foundation models by returning the token count that would be used if the same input were sent to the model in an inference request.

Token counting is model-specific because different models use different tokenization strategies. The token count returned by this operation will match the token count that would be charged if the same input were sent to the model in an InvokeModel or Converse request.

You can use this operation to:

Estimate costs before sending inference requests.
Optimize prompts to fit within token limits.
Plan for token usage in your applications.

This operation accepts the same input formats as InvokeModel and Converse, allowing you to count tokens for both raw text inputs and structured conversation formats.

The following operations are related to CountTokens:

InvokeModel - Sends inference requests to foundation models
Converse - Sends conversation-based inference requests to foundation models

Request Syntax


POST /model/modelId/count-tokens HTTP/1.1
Content-type: application/json

{
   "input": { ... }
}

URI Request Parameters

The request uses the following URI parameters.

modelId

The unique identifier or ARN of the foundation model to use for token counting. Each model processes tokens differently, so the token count is specific to the model you specify.

Length Constraints: Minimum length of 1. Maximum length of 256.

Pattern: [a-zA-Z_\.\-/0-9:]+

Required: Yes

Request Body

The request accepts the following data in JSON format.

input

The input for which to count tokens. The structure of this parameter depends on whether you're counting tokens for an InvokeModel or Converse request:

For InvokeModel requests, provide the request body in the invokeModel field
For Converse requests, provide the messages and system content in the converse field

The input format must be compatible with the model specified in the modelId parameter.

Type: CountTokensInput object

Note: This object is a Union. Only one member of this object can be specified or returned.

Required: Yes

Response Syntax


HTTP/1.1 200
Content-type: application/json

{
   "inputTokens": number
}

Response Elements

If the action is successful, the service sends back an HTTP 200 response.

The following data is returned in JSON format by the service.

inputTokens

The number of tokens in the provided input according to the specified model's tokenization rules. This count represents the number of input tokens that would be processed if the same input were sent to the model in an inference request. Use this value to estimate costs and ensure your inputs stay within model token limits.

Type: Integer

Errors

For information about the errors that are common to all actions, see Common Errors.

AccessDeniedException

The request is denied because you do not have sufficient permissions to perform the requested action. For troubleshooting this error, see AccessDeniedException in the Amazon Bedrock User Guide

HTTP Status Code: 403

InternalServerException

An internal server error occurred. For troubleshooting this error, see InternalFailure in the Amazon Bedrock User Guide

HTTP Status Code: 500

ResourceNotFoundException

The specified resource ARN was not found. For troubleshooting this error, see ResourceNotFound in the Amazon Bedrock User Guide

HTTP Status Code: 404

ServiceUnavailableException

The service isn't currently available. For troubleshooting this error, see ServiceUnavailable in the Amazon Bedrock User Guide

HTTP Status Code: 503

ThrottlingException

Your request was denied due to exceeding the account quotas for Amazon Bedrock. For troubleshooting this error, see ThrottlingException in the Amazon Bedrock User Guide

HTTP Status Code: 429

ValidationException

The input fails to satisfy the constraints specified by Amazon Bedrock. For troubleshooting this error, see ValidationError in the Amazon Bedrock User Guide

HTTP Status Code: 400