Open-Meteo vs Stormglass API

Open-Meteo

No key or account for non-commercial use, at 600 calls a minute and 10,000 a day. Commercial prices appear only at Stripe checkout.

Stormglass API

A read-only weather and marine API with about 70 hourly parameters, per-source values from named national models, tide data and ERA5 history from 2014. No OpenAPI file, status page, SDK or security page was found, the free plan allows 10 requests a day, and the docs and FAQ disagree on the status code for a spent quota.

Open-Meteo

1. Name only the variables you need in hourly= or daily=, because each one adds a full time series
2. Credit 'Weather data by Open-Meteo.com' wherever you show the data
3. Use customer-api.open-meteo.com with &apikey= for anything commercial, and keep that URL out of logs
4. Read reason on a 400. It names the bad parameter
5. Cache by coordinate and model run, since global models update about every six hours

Stormglass API

1. Send the key as Authorization: KEY with no Bearer prefix. A missing or wrong key returns 403 with {"errors":{"key":"API key is invalid"}}
2. Always pass source=sg or a short source list on /weather/point. The default is every source, which multiplies the size of each hourly record
3. Treat 402 as a spent daily quota, not a billing failure, and stop until the next day. Read meta.requestCount against meta.dailyQuota on each response
4. Use /historical/point for past dates, at most 10 days a call and nothing newer than about 7 days. /weather/point looks back 14 days only
5. Send and read all times in UTC. Tide sea levels are relative to the chosen datum (MSL by default) and are not water depth