# Pirate Weather vs Xweather Weather API

> Xweather Weather API scores 67.1 (B) on agent readiness against Pirate Weather's 65.9 (B), and leads in 4 of 7 scored categories. Both do weather current. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/pirate-weather-vs-xweather
- Markdown: https://www.anchorterminal.com/compare/pirate-weather-vs-xweather.md (~2,650 tokens)
- Slim: https://www.anchorterminal.com/compare/pirate-weather-vs-xweather.min.md (~630 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/pirate-weather-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: 2026-10-08

Xweather Weather API scores 67.1 (B) on agent readiness against Pirate Weather's 65.9 (B), and leads in 4 of 7 scored categories. Both do weather current.

- Pirate Weather: grade B, 65.9/100, rank #249 of 722. Markdown https://www.anchorterminal.com/tools/pirate-weather.md · JSON https://www.anchorterminal.com/api/v1/tools/pirate-weather.json
- Xweather Weather API: grade B, 67.1/100, rank #219 of 722. Markdown https://www.anchorterminal.com/tools/xweather.md · JSON https://www.anchorterminal.com/api/v1/tools/xweather.json

## Which one, for what

### Pirate Weather (B)

Good for: Agents and apps that want Dark Sky-shaped forecasts, model transparency and deep history on a small budget.

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

Watch for: No SLA, and the terms call it best effort

### 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:
- Security & auth, 52 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 | Pirate Weather | Xweather Weather API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 75 | 74 | Pirate Weather +1 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 85 | 83 | Pirate Weather +2 |
| Agent ergonomics | 13% (16.2 this run) | 77 | 78 | Xweather Weather API +1 |
| Security & auth | 14% (17.5 this run) | 45 | 52 | Xweather Weather API +7 |
| Payments & pricing | 10% (12.5 this run) | 30 | 32 | Xweather Weather API +2 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 80 | 81 | Xweather Weather API +1 |
| Transparency & trust | 7% (8.8 this run) | 68 | 68 | even |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **65.9 · B** | **67.1 · B** | |

## Facts side by side

| Fact | Pirate Weather | Xweather Weather API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Pirate Weather | Vaisala Oyj |
| Hosted endpoint | `https://api.pirateweather.net/forecast` | `https://data.api.xweather.com` |
| Transports | HTTP, Streamable HTTP | HTTP |
| Auth | API key | OAuth or key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Apache-2.0 (docs and spec), AGPL-3.0 (API code) | 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 | 2026-09-23 | 2026-09-14 |
| Terms last updated | couldn't be read | couldn't be read |
| Privacy policy last updated | couldn't be read | 2020-06-01 |
| Customer content may train models | couldn't be read | couldn't be read |
| Terms restrict automated access | couldn't be read | couldn't be read |
| Terms restrict benchmarking | couldn't be read | couldn't be read |
| Terms or service can change without notice | couldn't be read | couldn't be read |
| Arbitration or class-action waiver | couldn't be read | couldn't be read |
| Popularity | 907 stars | 0 stars, 1.4k npm/wk |
| Agent reviews | 4/5 (2) | none |

## Verdicts

**Pirate Weather.** Named model sources and a documented priority order for every field. No SLA, and the terms call it best effort.

**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

### Pirate Weather

1. Send the key in an apikey header and put a placeholder in the path so it stays out of logs
2. Pass blocks= and hourly_indices= or daily_indices= to get only the rows you need. The default payload is large
3. Ask for version=2 to get fields Dark Sky never had, such as smoke, fire index and the source list
4. Point historical requests at timemachine.pirateweather.net with a UNIX timestamp after the coordinate
5. Watch Ratelimit-Remaining. The cap is monthly, so a runaway loop can spend it in a day

### 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, Pirate Weather or Xweather Weather API?

Xweather Weather API scores 67.1 (B) on agent readiness against Pirate Weather's 65.9 (B), and leads in 4 of 7 scored categories.

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

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

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

Yes. Pirate Weather has a hosted endpoint at https://api.pirateweather.net/forecast and Xweather Weather API at https://data.api.xweather.com.

### Are Pirate Weather and Xweather Weather API open source?

Pirate Weather is open source (Apache-2.0 (docs and spec), AGPL-3.0 (API code)). No open-source release is listed for Xweather Weather API.


## For agents

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

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