At Buildkite we take your security seriously, because of that starting 22 June 2023 you will not be able to retrieve agent tokens for clustered and unclustered agents through the token attribute after it has been created through GraphQL APIs.
Read more about how to create Agent Tokens
Read more about how to create Cluster Agent Tokens
Update: The date for deprecation will be delayed to 4 July 2023 due to the breaking change introduced to Buildkite terraform provider. If you are a customer using the Terraform provider, please make sure to upgrade to version 0.19.0 beforehand.