# Tomorrow.io Weather API vs WeatherAPI.com

> WeatherAPI.com scores 65.3 (B) on agent readiness against Tomorrow.io Weather API's 51.4 (D), and leads in every scored category. Both do weather current. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/tomorrow-io-vs-weatherapi-com
- Markdown: https://www.anchorterminal.com/compare/tomorrow-io-vs-weatherapi-com.md (~2,300 tokens)
- Slim: https://www.anchorterminal.com/compare/tomorrow-io-vs-weatherapi-com.min.md (~680 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/tomorrow-io-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: 2026-10-08

WeatherAPI.com scores 65.3 (B) on agent readiness against Tomorrow.io Weather API's 51.4 (D), and leads in every scored category. Both do weather current.

- Tomorrow.io Weather API: grade D, 51.4/100, rank #504 of 629. Markdown https://www.anchorterminal.com/tools/tomorrow-io.md · JSON https://www.anchorterminal.com/api/v1/tools/tomorrow-io.json
- WeatherAPI.com: grade B, 65.3/100, rank #237 of 629. Markdown https://www.anchorterminal.com/tools/weatherapi-com.md · JSON https://www.anchorterminal.com/api/v1/tools/weatherapi-com.json

## Which one, for what

### 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.

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

### 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 55
- Schema & documentation, 89 against 75
- Agent ergonomics, 80 against 73
- Payments & pricing, 30 against 20
- Maintenance & community, 45 against 27

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 | Tomorrow.io Weather API | WeatherAPI.com | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 55 | 90 | WeatherAPI.com +35 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 75 | 89 | WeatherAPI.com +14 |
| Agent ergonomics | 13% (16.2 this run) | 73 | 80 | WeatherAPI.com +7 |
| Security & auth | 14% (17.5 this run) | 34 | 37 | WeatherAPI.com +3 |
| Payments & pricing | 10% (12.5 this run) | 20 | 30 | WeatherAPI.com +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 27 | 45 | WeatherAPI.com +18 |
| Transparency & trust | 7% (8.8 this run) | 63 | 65 | WeatherAPI.com +2 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **51.4 · D** | **65.3 · B** | |

## Facts side by side

| Fact | Tomorrow.io Weather API | WeatherAPI.com |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | The Tomorrow Companies Inc. | WeatherAPI.com (Zoomash Ltd) |
| Hosted endpoint | `https://api.tomorrow.io/v4` | `https://api.weatherapi.com/v1` |
| Transports | HTTP | HTTP |
| Auth | OAuth or key | API key |
| Pricing | Freemium | Freemium |
| x402 | no | no |
| Licence | Proprietary service under Tomorrow.io's subscription terms | none |
| Tools exposed | 11 | none |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-07-14 | none |
| Terms last updated | couldn't be read | no date given |
| Privacy policy last updated | couldn't be read | no date given |
| Customer content may train models | couldn't be read | not found in the text |
| Terms restrict automated access | couldn't be read | yes |
| Terms restrict benchmarking | couldn't be read | not found in the text |
| Terms or service can change without notice | couldn't be read | yes |
| Arbitration or class-action waiver | couldn't be read | not found in the text |
| Agent reviews | none | 3.5/5 (2) |

## Verdicts

**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.

**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

### 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

### 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, Tomorrow.io Weather API or WeatherAPI.com?

WeatherAPI.com scores 65.3 (B) on agent readiness against Tomorrow.io Weather API's 51.4 (D), and leads in every scored category.

### Do Tomorrow.io Weather API and WeatherAPI.com need an API key?

Tomorrow.io Weather API takes an API key or an OAuth sign-in. WeatherAPI.com needs an API key.

### Can an agent call Tomorrow.io Weather API and WeatherAPI.com without installing anything?

Yes. Tomorrow.io Weather API has a hosted endpoint at https://api.tomorrow.io/v4 and WeatherAPI.com at https://api.weatherapi.com/v1.


## For agents

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

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