carbon.txt, described using TOML. TOML is human and machine readable, flexible, and allows comments.

more-likely.toml

# general principle - make it easy to find sustainability claims made by orgs, so you can understand what
# they are doing, but also make it easy to find the supporting evidence for the claims being made
# to avoid accusations of greenwash

[upstream]
providers =  [ 

  # these folks haven't implemented carbon.txt, and there isn't information listed by them yet,
  # but you know they have some information online, and you want to point to it.
  # you've listed it here, and when the TGWF scraper bot visits the page, it adds it to the list
  # of claims and evidence provided by them. 
  # To prevent abuse, syseleven are able to refute or correct the claim. If the claim was confirmed by syseleven,
  # this would show when looking up the site, so you can see the sustainability info from bergfreunde primarily,
  # but also the upstream providers used. If you have chosen a greener provider, it should be recognised.

  { domain = 'syseleven.com', doctype = 'sustainability-page', url = 'https://www.syseleven.de/en/about-us/our-data-centers/' }
]

[org]
credentials =  [
  # for this domain, the key information you would share when someone is trying to understand how 'green' an 
  # organisation would be listed here.
  { domain = 'www.bergfreunde.de', doctype = 'sustainability-page', url = 'https://www.bergfreunde.de/klimaneutral/' },
  { domain = 'www.bergfreunde.de', doctype = 'carbon-compensation', url = 'https://fpm.climatepartner.com/tracking/13467-1912-1001/en' }
]

the-minimal-ideal.toml

# general principle - make it easy to find sustainability claims made by orgs, so you can understand what
# they are doing, but also make it easy to find the supporting evidence for the claims being made
# to avoid accusations of greenwash

[upstream]
providers =  [ 

  # in this scenario, these folks already are listed in the green web foundation directory,
  # and have implemented a carbon.txt linking to 
  # the good stuff they do, along with underlying evidence to support their claims.
  # Alternatively, they have already uploaded the similar evidence and claims to the TGWF database
  'fictional-green-hosting.com',
]

[org]
credentials =  [
  # for this domain, the key information you would share when someone is trying to understand how 'green' an 
  # organisation would be listed here.
  { domain = 'www.bergfreunde.de', doctype = 'sustainability-page', url = 'https://www.bergfreunde.de/klimaneutral/' },
  { domain = 'www.bergfreunde.de', doctype = 'carbon-compensation', url = 'https://fpm.climatepartner.com/tracking/13467-1912-1001/en' }
]