This tool will accept a run ID and a token, and optionally a directory to store things. The directory and token(and base_url in case it's needed for TFE) can be stored in a config file.

It will get the plan ID

from the response object
of the 'get run details' API call:
https://developer.hashicorp.com/terraform/cloud-docs/api-docs/run#get-run-details

Then, it will make a request to plan exports.

First, it will create a plan export:
https://developer.hashicorp.com/terraform/cloud-docs/api-docs/plan-exports#download-exported-plan-data

The response will contain a plan export ID, something like "pe-1jasfkl4lads86f"

You can then monitor the `data.attributes.status` for when it is `finished`

The response will contain a link to the download URL:
`data.attributes.links`

Then, the exported data will be downloaded (either in the current directory or wherever specified):
https://developer.hashicorp.com/terraform/cloud-docs/api-docs/plan-exports#download-exported-plan-data