# Stormglass API vs Xweather Weather API

> Xweather Weather scores 67.1 (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-xweather
- Markdown: https://www.anchorterminal.com/compare/stormglass-vs-xweather.md (~2,900 tokens)
- Slim: https://www.anchorterminal.com/compare/stormglass-vs-xweather.min.md (~780 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/stormglass-vs-xweather.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

Xweather Weather API scores 67.1 (B) on agent readiness against Stormglass API's 39.9 (E), and leads in every scored category. 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
- Xweather Weather API: grade B, 67.1/100, rank #265 of 950. Markdown https://www.anchorterminal.com/tools/xweather.md · JSON https://www.anchorterminal.com/api/v1/tools/xweather.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.

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

### Xweather Weather API (B)

Good for: Teams that need lightning, hail, road weather or tropical data beside ordinary conditions and forecasts, with an MCP server and an OpenAPI file ready for agents.

Ahead on:
- Reliability, 74 against 34
- Schema & documentation, 83 against 40
- Agent ergonomics, 78 against 65
- Security & auth, 52 against 44
- Payments & pricing, 32 against 25
- Maintenance & community, 81 against 15
- Transparency & trust, 68 against 45

Watch for: The REST API documents `client_id` and `client_secret` only as query parameters, and the MCP server also accepts the key as `?api_key=`


## Score by category

| Category | Weight | Stormglass API | Xweather Weather API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 34 | 74 | Xweather Weather API +40 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 40 | 83 | Xweather Weather API +43 |
| Agent ergonomics | 13% (16.2 this run) | 65 | 78 | Xweather Weather API +13 |
| Security & auth | 14% (17.5 this run) | 44 | 52 | Xweather Weather API +8 |
| Payments & pricing | 10% (12.5 this run) | 25 | 32 | Xweather Weather API +7 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 15 | 81 | Xweather Weather API +66 |
| Transparency & trust | 7% (8.8 this run) | 45 | 68 | Xweather Weather API +23 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **39.9 · E** | **67.1 · B** | |

## Facts side by side

| Fact | Stormglass API | Xweather Weather API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Storm Glass AB | Vaisala Oyj |
| Hosted endpoint | `https://api.stormglass.io/v2` | `https://data.api.xweather.com` |
| Transports | HTTP | HTTP |
| Auth | API key | OAuth or 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 | Proprietary service under the General Conditions of Subscription Services of Vaisala Group. The OpenAPI files and the agent skills on GitHub are MIT |
| Tools exposed | none | 19 |
| Read-only variant documented | no | no |
| llms.txt | no | yes |
| MCP registry | not listed | `com.xweather/weather` |
| Last release | 2026-02-26 | 2026-09-14 |
| Terms last updated | no date given | couldn't be read |
| Privacy policy last updated | no date given | 2020-06-01 |
| Customer content may train models | not found in the text | couldn't be read |
| Terms restrict automated access | not found in the text | couldn't be read |
| Terms restrict benchmarking | not found in the text | couldn't be read |
| Terms or service can change without notice | yes | couldn't be read |
| Arbitration or class-action waiver | yes | couldn't be read |
| Popularity | none | 0 stars, 1.4k npm/wk |

## 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.

**Xweather Weather API.** A public OpenAPI file with 236 operations, a hosted MCP server in the official registry and a free tier of 15,000 accesses a month suit agents. REST credentials travel only in the query string, per-minute limits are unpublished, and the group terms bar commercial use of free plans and passing data to third parties unless a service description allows it.

## 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

### Xweather Weather API

1. Check `success` and `error.code` on every response. Application errors such as `invalid_location` return HTTP 200 with `success` false
2. Send `fields`, `limit` and `plimit`. The docs put a 15-day hourly forecast at about 600 KB, and about 25 KB with three fields
3. Read `X-Cost-Tokens` after each call. Cost is the endpoint multiplier times the intervals requested, so narrow `from` and `to`
4. For MCP, send `Authorization: Bearer <client_id>_<client_secret>` and avoid the `api_key` query parameter, which puts the secret in the URL
5. Add `include_tags` or `include_tools` to the MCP URL to load only the tool groups the task needs
6. On 429 read `Retry-After` and the `X-RateLimit-Reset-*` headers. `maxhits_min` clears at the next minute, `maxhits` at the period reset

## Questions

### Which is better for AI agents, Stormglass API or Xweather Weather API?

Xweather Weather API scores 67.1 (B) on agent readiness against Stormglass API's 39.9 (E), and leads in every scored category.

### Do Stormglass API and Xweather Weather API need an API key?

Stormglass API needs an API key. Xweather Weather API takes an API key or an OAuth sign-in.

### Can an agent call Stormglass API and Xweather Weather API without installing anything?

Yes. Stormglass API has a hosted endpoint at https://api.stormglass.io/v2 and Xweather Weather API at https://data.api.xweather.com.


## For agents

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

## Other comparisons with Stormglass API or Xweather Weather API

- [AccuWeather Core Weather API + MCP vs Xweather Weather API](https://www.anchorterminal.com/compare/accuweather-api-vs-xweather.md)
- [Google Weather API (Maps Platform) vs Xweather Weather API](https://www.anchorterminal.com/compare/google-weather-api-vs-xweather.md)
- [Met Office Weather DataHub (Site Specific) vs Xweather Weather API](https://www.anchorterminal.com/compare/met-office-datahub-vs-xweather.md)
- [meteoblue Weather API vs Xweather Weather API](https://www.anchorterminal.com/compare/meteoblue-vs-xweather.md)
- [Meteomatics Weather API vs Xweather Weather API](https://www.anchorterminal.com/compare/meteomatics-vs-xweather.md)
- [NOAA National Weather Service API (api.weather.gov) vs Xweather Weather API](https://www.anchorterminal.com/compare/nws-api-vs-xweather.md)
- [OpenWeather One Call API vs Xweather Weather API](https://www.anchorterminal.com/compare/openweather-one-call-vs-xweather.md)
- [Pirate Weather vs Xweather Weather API](https://www.anchorterminal.com/compare/pirate-weather-vs-xweather.md)
- [Tomorrow.io Weather API vs Xweather Weather API](https://www.anchorterminal.com/compare/tomorrow-io-vs-xweather.md)
- [Visual Crossing Weather API vs Xweather Weather API](https://www.anchorterminal.com/compare/visual-crossing-vs-xweather.md)
- [The Weather Company Data APIs vs Xweather Weather API](https://www.anchorterminal.com/compare/weather-company-vs-xweather.md)
- [WeatherAPI.com vs Xweather Weather API](https://www.anchorterminal.com/compare/weatherapi-com-vs-xweather.md)
- [Weatherbit API vs Xweather Weather API](https://www.anchorterminal.com/compare/weatherbit-vs-xweather.md)
- [Open-Meteo vs Stormglass API](https://www.anchorterminal.com/compare/open-meteo-vs-stormglass.md)
- [Open-Meteo vs Xweather Weather API](https://www.anchorterminal.com/compare/open-meteo-vs-xweather.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)
- [Meteomatics Weather API vs Stormglass API](https://www.anchorterminal.com/compare/meteomatics-vs-stormglass.md)
- [NOAA National Weather Service API (api.weather.gov) vs Stormglass API](https://www.anchorterminal.com/compare/nws-api-vs-stormglass.md)
- [OpenWeather One Call API vs Stormglass API](https://www.anchorterminal.com/compare/openweather-one-call-vs-stormglass.md)
- [Pirate Weather vs Stormglass API](https://www.anchorterminal.com/compare/pirate-weather-vs-stormglass.md)
- [Stormglass API vs Tomorrow.io Weather API](https://www.anchorterminal.com/compare/stormglass-vs-tomorrow-io.md)
- [Stormglass API vs Visual Crossing Weather API](https://www.anchorterminal.com/compare/stormglass-vs-visual-crossing.md)
- [Stormglass API vs The Weather Company Data APIs](https://www.anchorterminal.com/compare/stormglass-vs-weather-company.md)
- [Stormglass API vs WeatherAPI.com](https://www.anchorterminal.com/compare/stormglass-vs-weatherapi-com.md)
- [Stormglass API vs Weatherbit API](https://www.anchorterminal.com/compare/stormglass-vs-weatherbit.md)