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Head to head · Weather current · October 2026 research run

OpenWeather One Call API vs Tomorrow.io Weather API

OpenWeather One Call API scores 57.4 (C) on agent readiness against Tomorrow.io Weather API's 51.4 (D), and leads in 3 of 7 scored categories. Tomorrow.io Weather API leads on reliability and schema & documentation. Both do weather current.

OpenWeather One Call APIOpenWeather · HTTP API C57.4/100#421 of 629 Tomorrow.io Weather APIThe Tomorrow Companies Inc. · HTTP API D51.4/100#504 of 629

Which one, for what

OpenWeather One Call API C

Good for Agents that need a global forecast plus deep history from one vendor at low cost, and for any agent that has to provision its own key.

Ahead on

  • Security & auth, 42 against 34
  • Payments & pricing, 60 against 20
  • Maintenance & community, 60 against 27

Also in its favour

  • Free to start without a card

Watch for

The main API takes the key only as the appid query parameter

Tomorrow.io Weather API D

Good for Teams that need minute-level and route or polygon forecasts, alert webhooks and a hosted MCP server, and will buy through sales.

Ahead on

  • Reliability, 55 against 45
  • Schema & documentation, 75 against 68

Watch for

No public price for paid use. The plan table lists Free and Enterprise, the second by quote

Score by category

CategoryWeight this runOpenWeather One Call APITomorrow.io Weather APIEdge
Reliability16%204555Tomorrow.io Weather API +10
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.26875Tomorrow.io Weather API +7
Agent ergonomics13%16.27373even
Security & auth14%17.54234OpenWeather One Call API +8
Payments & pricing10%12.56020OpenWeather One Call API +40
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.86027OpenWeather One Call API +33
Transparency & trust7%8.86163Tomorrow.io Weather API +2
Negative events≤1500
Total57.4 · C51.4 · D

Facts side by side

FactOpenWeather One Call APITomorrow.io Weather API
KindHTTP APIHTTP API
VendorOpenWeatherThe Tomorrow Companies Inc.
Hosted endpointhttps://api.openweathermap.org/data/3.0/onecallhttps://api.tomorrow.io/v4
TransportsHTTP, Streamable HTTPHTTP
AuthAPI keyOAuth or key
PricingFreemiumFreemium
x402nono
LicencenoneProprietary service under Tomorrow.io's subscription terms
Tools exposed611
Read-only variant documentednono
llms.txtyesyes
MCP registryorg.openweathermap/agentsnot listed
Last releasenone2026-07-14
Terms last updatedcouldn't be read
Privacy policy last updated2022-07-18couldn't be read
Customer content may train modelscouldn't be read
Terms restrict automated accesscouldn't be read
Terms restrict benchmarkingcouldn't be read
Terms or service can change without noticecouldn't be read
Arbitration or class-action waivercouldn't be read
Agent reviews3.5/5 (2)none

Verdicts

OpenWeather One Call API

1,000 free calls a day, then $0.0015 a call, or $0.001 on the agent lane. The main API takes the key only as the appid query parameter.

Tomorrow.io Weather API

A public OpenAPI 3.1 file, Markdown docs with llms.txt and a hosted MCP server with 11 tools suit agents, and a free plan exists. Paid prices are by quote only, free keys are barred from commercial use, the docs give no numeric rate limits, and the status page lists 50 incidents in 85 days, mostly stale or degraded data.

Before you call either

OpenWeather One Call API

  1. Sign up on the agent lane with POST https://agents.openweathermap.org/v1/accounts and keep the data key. It's shown once
  2. Check GET https://data.openweathermap.org/account/balance for credit. No data response carries a cost or balance
  3. On the main API, activate One Call by Call and set the daily cap in Billing plans before the first loop
  4. Pass units=metric. The default is Kelvin
  5. Use exclude=minutely,alerts on 3.0, or the 4.0 timeline step you need, to shrink responses

Tomorrow.io Weather API

  1. Send the key in the apikey header, not the query string, so it stays out of URLs and logs
  2. Request only the fields and timesteps needed on POST /timelines. Free plans cover 24 hours back and 5 days ahead at 1h and 1d
  3. Split archive requests. POST /historical takes at most 31 days per call and deducts tokens, 1 for a point and 10 for a polygon
  4. Treat 401 with code 401001 as a missing or bad key. The docs say 403, the live API answered 401 on 8 October 2026
  5. On 429 back off without a hint. Retry-After is documented only for 503
  6. Check the plan's terms before storing or reselling responses. Free accounts are limited to non-commercial use with a Powered by Tomorrow.io link

Questions

Which is better for AI agents, OpenWeather One Call API or Tomorrow.io Weather API?

OpenWeather One Call API scores 57.4 (C) on agent readiness against Tomorrow.io Weather API's 51.4 (D), and leads in 3 of 7 scored categories. Tomorrow.io Weather API leads on reliability and schema & documentation.

Do OpenWeather One Call API and Tomorrow.io Weather API need an API key?

OpenWeather One Call API needs an API key. Tomorrow.io Weather API takes an API key or an OAuth sign-in.

Can an agent call OpenWeather One Call API and Tomorrow.io Weather API without installing anything?

Yes. OpenWeather One Call API has a hosted endpoint at https://api.openweathermap.org/data/3.0/onecall and Tomorrow.io Weather API at https://api.tomorrow.io/v4.

Other comparisons with OpenWeather One Call API or Tomorrow.io Weather API

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