Unable to submit (resubmit?) use case for model access

I'm trying to automate the use case submission for accessing Anthropic models in AWS Bedrock.

I'm attempting to submit formData using the AWS CLI (and boto3 library). In all cases I'm getting the following error: An error occurred (ValidationException) when calling the PutUseCaseForModelAccess operation: Invalid form data.

I've reduced this to re-submitting the data that's already been submitted using aws bedrock put-use-case-for-model-access --form-data <data> where comes from the formData field output by aws bedrock get-use-case-for-model-access --profile prod.

I note that when using the CLI (although not boto3) that the formData is double encoded so I need to use aws bedrock get-use-case-for-model-access --profile prod --region eu-west-1 --query formData --output text | base64 -D | base64 -D to get the original form (note base64 -D twice).

Can you help me figure out what is going on?

• I've tried submitting to accounts which have previously had a use case submitted and also accounts which have not.
• I've tried submitting formData double encoded (as it arrives) and single encoded (as it arrives via boto3).
• I've tried filling in the form in another AWS account via the console and submitting that whilst the network of my machine is disabled so I can capture the payload and use that payload via the CLI. That also doesn't seem to work.
• I've submitted to eu-west-1

I'm kind of operating blind without having found any documentation that details the valid shape.

After a lot of experimentation I found that:

• this endpoint only works in us-east-1 (it is global)
• that the formData must be base64 encoded only once for CLI submission and not base64 encoded at all when doing this via boto3
• that the shape is as below

{"companyName":"","companyWebsite":"","intendedUsers":"0","industryOption":"","otherIndustryOption":"","useCases":""} where intendedUsers is 0 for internal and industryOption should be the value from the drop down in the form.

Note/warning: As far as I can tell, this is a one-off operation. Re-submitting a use-case does not update it.