---
title: "PUT /evaluators/{evaluatorId}"
method: PUT
path: "/evaluators/{evaluatorId}"
---

# PUT /evaluators/{evaluatorId}

`PUT /evaluators/{evaluatorId}`

Updates a custom evaluator's configuration, description, or evaluation level. Built-in evaluators cannot be updated. The evaluator must not be locked for modification.

## Path parameters

- `evaluatorId` string, required

## Request body

- object
  - `clientToken` string — A unique, case-sensitive identifier to ensure that the API request completes no more than one time. If you don't specify this field, a value is randomly generated for you. If this token matches a previous request, the service ignores the request, but doesn't return an error. For more information, see <a href="https://docs.aws.amazon.com/AWSEC2/latest/APIReference/Run_Instance_Idempotency.html">Ensuring idempotency</a>.
  - `description` string, password — The updated description of the evaluator.
  - `evaluatorConfig` object — The configuration that defines how an evaluator assesses agent performance, including the evaluation method and parameters.
    - `llmAsAJudge` object — The LLM-as-a-Judge configuration that uses a language model to evaluate agent performance based on custom instructions and rating scales.
      - `instructions` string, password, required — The evaluation instructions that guide the language model in assessing agent performance, including criteria and evaluation guidelines.
      - `ratingScale` object, required — The rating scale that defines how the evaluator should score agent performance, either numerical or categorical.
        - `numerical` NumericalScaleDefinition[] — The numerical rating scale with defined score values and descriptions for quantitative evaluation.
          - `definition` string, required — The description that explains what this numerical rating represents and when it should be used.
          - `value` number, double, required — The numerical value for this rating scale option.
          - `label` string, required — The label or name that describes this numerical rating option.
        - `categorical` CategoricalScaleDefinition[] — The categorical rating scale with named categories and definitions for qualitative evaluation.
          - `definition` string, required — The description that explains what this categorical rating represents and when it should be used.
          - `label` string, required — The label or name of this categorical rating option.
      - `modelConfig` object, required — The model configuration that specifies which foundation model to use and how to configure it for evaluation.
        - `bedrockEvaluatorModelConfig` object — The Amazon Bedrock model configuration for evaluation.
          - `modelId` string, required — The identifier of the Amazon Bedrock model to use for evaluation. Must be a supported foundation model available in your region.
          - `inferenceConfig` object — The inference configuration parameters that control model behavior during evaluation, including temperature, token limits, and sampling settings.
            - `maxTokens` integer — The maximum number of tokens to generate in the model response during evaluation.
            - `temperature` number, float — The temperature value that controls randomness in the model's responses. Lower values produce more deterministic outputs.
            - `topP` number, float — The top-p sampling parameter that controls the diversity of the model's responses by limiting the cumulative probability of token choices.
            - `stopSequences` NonEmptyString[] — The list of sequences that will cause the model to stop generating tokens when encountered.
          - `additionalModelRequestFields` object — Additional model-specific request fields to customize model behavior beyond the standard inference configuration.
    - `codeBased` object — Configuration for a code-based evaluator that uses a customer-managed Lambda function to programmatically assess agent performance.
      - `lambdaConfig` object — The Lambda function configuration for code-based evaluation.
        - `lambdaArn` string, required — The Amazon Resource Name (ARN) of the Lambda function that implements the evaluation logic.
        - `lambdaTimeoutInSeconds` integer — The timeout in seconds for the Lambda function invocation. Defaults to 60. Must be between 1 and 300.
  - `level` 'TOOL_CALL' | 'TRACE' | 'SESSION' — The updated evaluation level (<code>TOOL_CALL</code>, <code>TRACE</code>, or <code>SESSION</code>) that determines the scope of evaluation.
  - `kmsKeyArn` string — The Amazon Resource Name (ARN) of a customer managed KMS key to use for encrypting sensitive evaluator data. Specify a new key ARN to rotate the encryption key, or specify a key ARN to add encryption to an evaluator that was previously created without one. When you rotate to a new key, the service decrypts the existing data with the old key and re-encrypts it with the new key. Only symmetric encryption KMS keys are supported. For more information, see <a href="https://docs.aws.amazon.com/bedrock-agentcore/latest/devguide/evaluations-encryption.html">Encryption at rest for AgentCore Evaluations</a>.

## Response `202`

Success

- UpdateEvaluatorResponse
  - `evaluatorArn` string, required — The Amazon Resource Name (ARN) of the updated evaluator.
  - `evaluatorId` string, required — The unique identifier of the updated evaluator.
  - `updatedAt` string, date-time, required — The timestamp when the evaluator was last updated.
  - `status` 'ACTIVE' | 'CREATING' | 'CREATE_FAILED' | 'UPDATING' | 'UPDATE_FAILED' | 'DELETING', required — The status of the evaluator update operation.

## Other responses

- `480` — ServiceQuotaExceededException
- `481` — ValidationException
- `482` — AccessDeniedException
- `483` — ConflictException
- `484` — ResourceNotFoundException
- `485` — ThrottlingException
- `486` — InternalServerException

---

[API](https://skmtc.net/aws/apis/bedrock-agentcore-control.md) · [All operations](https://skmtc.net/aws/apis/bedrock-agentcore-control/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/aws/bedrock-agentcore-control/versions/0ebde766792b/schema)