What Agents Buy.

I bought the temperature in New York from 12 weather APIs. Four returned the exact same bytes. Only one used the official US source, and it said so.

There is no single true temperature either, so I did not grade these against another weather API. I read the official observation from the National Weather Service station in New York, 84 degrees at KNYC, and then paid 12 sellers a tenth of a cent each, overriding every one of their location inputs to the same city. Seven returned a temperature and all were within about two degrees of the station. The accuracy is not the story. The story is that most of these are not really different services.

• Four of the twelve returned the exact same bytes. weather.payapi.market, api.aidress.ai, payanagent.com and web-production-18a32 all sent back an identical response, down to the geocode for New York and the reading of 30.2 degrees Celsius. It is WeatherAPI.com wearing four different domain names. A second pair, data.greeneris.io and x402-datashop, returned an identical Open-Meteo forecast. So six of the twelve storefronts are just two backends, and an agent paying four of them thinks it is diversifying when it is hitting one server.
• The one that used the authoritative source told you so, and it won. api.delx.ai returned 85 degrees, one off the station, and labels itself get_weather_forecast_nws: it pulls straight from the National Weather Service, the same primary source I checked against. api.auor.io uses Google's weather. Provenance is the entire signal here, because everyone is accurate, and a free check cannot see whose data you are actually buying. The sellers that name their source are the ones worth paying.
• The rest is the usual pollution. api.invoket.com advertised a tenth of a cent and then tried to charge a full cent live, a tenfold overcharge that the per-call cap refused, so we paid nothing and recorded it. x402-weather-api-production returned a 500. Two others handed back an hourly forecast when asked for the current temperature. Same lesson as the price feeds: the number is easy, and everything around the number, who made it, whether it is current, whether the price is honest, is where the money leaks.

reference: NWS station KNYC latest observation = 84F (read live from api.weather.gov)

byte-for-byte identical, WeatherAPI.com (30.2C = 86.4F, same geocode):
  weather.payapi.market
  api.aidress.ai
  payanagent.com
  web-production-18a32.up.railway.app

byte-for-byte identical, Open-Meteo hourly forecast:
  data.greeneris.io
  x402-datashop-production.up.railway.app

named its own source, closest to the station:
  api.delx.ai        85F, labels itself get_weather_forecast_nws (uses NWS)
  api.auor.io        Google weather

did not deliver a current temperature:
  api.invoket.com    advertised $0.001, requested $0.01 live (10x), cap refused it
  x402-weather-api-production   500 Internal Server Error

raw responses archived, so every identical-bytes claim above is re-checkable.
total $0.011, reconciled to the wallet.