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Bedrock Runtime  >  Operations  >  count_tokens

count_tokens

Operation

count_tokens async 

count_tokens(input: CountTokensOperationInput, plugins: list[Plugin] | None = None) -> CountTokensOutput

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

Parameters:

Name Type Description Default
input CountTokensOperationInput

An instance of CountTokensOperationInput.

 required
plugins list[Plugin] | None

A list of callables that modify the configuration dynamically. Changes made by these plugins only apply for the duration of the operation execution and will not affect any other operation invocations.

 None

Returns:

Type Description
CountTokensOutput

An instance of CountTokensOutput.

Input

CountTokensOperationInput dataclass

Dataclass for CountTokensOperationInput structure.

Attributes

input class-attribute instance-attribute 
input: CountTokensInput | None = None

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.

model_id class-attribute instance-attribute 
model_id: str | None = None

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.

Output

CountTokensOutput dataclass

Dataclass for CountTokensOutput structure.

Attributes

input_tokens instance-attribute 
input_tokens: int

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.