FAQ

This FAQ covers two parameter issues reported by customers. The affected requests use AWS Bedrock Runtime underneath. The official support scope was checked on September 10, 2026. Model capabilities can change; check the latest AWS documentation for your target model.

Why does output_config.format return 400?

output_config.format: Extra inputs are not permitted

The request includes output_config.format to specify a structured output format. Bedrock Runtime supports Structured Outputs, but the specific model must support it too.

The Claude Sonnet 5 and Claude Opus 5 models used in this investigation are not currently listed as supporting Structured Outputs in the linked AWS documentation. The affected requests returned a 400 parameter error when output_config.format was included. This finding applies to the investigated requests; it does not mean Runtime lacks structured output support altogether.

What to do: Remove output_config.format when using these models. If your application requires Structured Outputs, verify AWS support for the target model and API, and confirm support through your current integration before switching. Asking for JSON in a prompt is not equivalent to schema-constrained structured output.

AWS documentation: Claude Messages: Structured Outputs.

Why does tool use report a missing toolConfig?

The toolConfig field must be defined when using toolUse and toolResult content blocks.

This error indicates that the request contains toolUse / toolResult content blocks without the corresponding toolConfig tool definitions. Check that your client request still includes the matching tools definitions. toolConfig is the Bedrock Converse field name; do not directly replace your client protocol's tools field with it.

Local comparison tests from this investigation showed that the request succeeded with tools and produced the same error after tools was removed.

What to do: Keep the corresponding tools definitions in follow-up requests, especially when returning tool results or resending conversation history that includes tool calls. Check whether your SDK or request wrapper sends tools only on the first turn and drops it on subsequent turns.

AWS documentation: Use a tool to complete an Amazon Bedrock model response.

See Error codes for more status codes.