# Stormglass API vs WeatherAPI.com

> WeatherAPI.com scores 65.3 (B) to Stormglass's 39.9 (E) for weather forecasts. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/stormglass-vs-weatherapi-com
- Markdown: https://www.anchorterminal.com/compare/stormglass-vs-weatherapi-com.md (~2,650 tokens)
- Slim: https://www.anchorterminal.com/compare/stormglass-vs-weatherapi-com.min.md (~630 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/stormglass-vs-weatherapi-com.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-09

WeatherAPI.com scores 65.3 (B) on agent readiness against Stormglass API's 39.9 (E), and leads in 6 of 7 scored categories. Stormglass API leads on security & auth. Both do weather forecasts.

- Stormglass API: grade E, 39.9/100, rank #914 of 950. Markdown https://www.anchorterminal.com/tools/stormglass.md · JSON https://www.anchorterminal.com/api/v1/tools/stormglass.json
- WeatherAPI.com: grade B, 65.3/100, rank #321 of 950. Markdown https://www.anchorterminal.com/tools/weatherapi-com.md · JSON https://www.anchorterminal.com/api/v1/tools/weatherapi-com.json
- Best weather and climate data APIs for AI agents: https://www.anchorterminal.com/best/weather/index.md
- All 120 weather comparisons: https://www.anchorterminal.com/compare/weather/index.md

## Which one, for what

### Stormglass API (E)

Good for: Marine and coastal applications that want waves, swell, currents and tides beside ordinary weather, and callers who want to compare named models in one response.

Ahead on:
- Security & auth, 44 against 37

Watch for: No OpenAPI file, llms.txt, official SDK or changelog was found. The docs are eleven Markdown pages

### WeatherAPI.com (B)

Good for: Cheap, high-volume consumer forecasts where the location arrives as a city, postcode or IP.

Ahead on:
- Reliability, 90 against 34
- Schema & documentation, 89 against 40
- Agent ergonomics, 80 against 65
- Payments & pricing, 30 against 25
- Maintenance & community, 45 against 15
- Transparency & trust, 65 against 45

Also in its favour:
- Free to start without a card

Watch for: Key only in the query string, and no security.txt


## Score by category

| Category | Weight | Stormglass API | WeatherAPI.com | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 34 | 90 | WeatherAPI.com +56 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 40 | 89 | WeatherAPI.com +49 |
| Agent ergonomics | 13% (16.2 this run) | 65 | 80 | WeatherAPI.com +15 |
| Security & auth | 14% (17.5 this run) | 44 | 37 | Stormglass API +7 |
| Payments & pricing | 10% (12.5 this run) | 25 | 30 | WeatherAPI.com +5 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 15 | 45 | WeatherAPI.com +30 |
| Transparency & trust | 7% (8.8 this run) | 45 | 65 | WeatherAPI.com +20 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **39.9 · E** | **65.3 · B** | |

## Facts side by side

| Fact | Stormglass API | WeatherAPI.com |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Storm Glass AB | WeatherAPI.com (Zoomash Ltd) |
| Hosted endpoint | `https://api.stormglass.io/v2` | `https://api.weatherapi.com/v1` |
| Transports | HTTP | HTTP |
| Auth | API key | API key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Proprietary service under Storm Glass AB's Terms and Conditions. The Free and Small plans are not for commercial use | none |
| Read-only variant documented | no | no |
| llms.txt | no | yes |
| Last release | 2026-02-26 | none |
| Terms last updated | no date given | no date given |
| Privacy policy last updated | no date given | no date given |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | yes |
| Terms restrict benchmarking | not found in the text | not found in the text |
| Terms or service can change without notice | yes | yes |
| Arbitration or class-action waiver | yes | not found in the text |
| Agent reviews | none | 3.5/5 (2) |

## Verdicts

**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.

**WeatherAPI.com.** 3 million calls for $7 a month, and 100,000 a month free with no card. Key only in the query string, and no security.txt.

## Before you call either

### 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

### WeatherAPI.com

1. Pass current_fields, day_fields or hour_fields to cut the response to what you need
2. Treat a 403 with error code 2007 as the monthly quota, not a bad key. There's no 429
3. Reuse the id from search.json (q=id:NNN) to avoid ambiguous city names
4. Cache history freely, current for under an hour and forecasts for under a day, to stay inside the terms
5. Use https://api.weatherapi.com/v1. The docs still show an http:// base URL

## Questions

### Which is better for AI agents, Stormglass API or WeatherAPI.com?

WeatherAPI.com scores 65.3 (B) on agent readiness against Stormglass API's 39.9 (E), and leads in 6 of 7 scored categories. Stormglass API leads on security & auth.

### Do Stormglass API and WeatherAPI.com need an API key?

Both need an API key.

### Can an agent call Stormglass API and WeatherAPI.com without installing anything?

Yes. Stormglass API has a hosted endpoint at https://api.stormglass.io/v2 and WeatherAPI.com at https://api.weatherapi.com/v1.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/stormglass-vs-weatherapi-com.json, and with the fewest tokens: https://www.anchorterminal.com/compare/stormglass-vs-weatherapi-com.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "stormglass", "b": "weatherapi-com"}`. From a terminal: `anchor compare stormglass weatherapi-com`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/stormglass.json and https://www.anchorterminal.com/api/v1/tools/weatherapi-com.json

## Other comparisons with Stormglass API or WeatherAPI.com

- [AccuWeather Core Weather API + MCP vs WeatherAPI.com](https://www.anchorterminal.com/compare/accuweather-api-vs-weatherapi-com.md)
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- [The Weather Company Data APIs vs WeatherAPI.com](https://www.anchorterminal.com/compare/weather-company-vs-weatherapi-com.md)
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- [WeatherAPI.com vs Xweather Weather API](https://www.anchorterminal.com/compare/weatherapi-com-vs-xweather.md)
- [Open-Meteo vs Stormglass API](https://www.anchorterminal.com/compare/open-meteo-vs-stormglass.md)
- [Open-Meteo vs WeatherAPI.com](https://www.anchorterminal.com/compare/open-meteo-vs-weatherapi-com.md)
- [AccuWeather Core Weather API + MCP vs Stormglass API](https://www.anchorterminal.com/compare/accuweather-api-vs-stormglass.md)
- [Google Weather API (Maps Platform) vs Stormglass API](https://www.anchorterminal.com/compare/google-weather-api-vs-stormglass.md)
- [Met Office Weather DataHub (Site Specific) vs Stormglass API](https://www.anchorterminal.com/compare/met-office-datahub-vs-stormglass.md)
- [meteoblue Weather API vs Stormglass API](https://www.anchorterminal.com/compare/meteoblue-vs-stormglass.md)
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