API Bridge — Curated Public API Toolkit for AI Agents

AI agents constantly need real-world data. This skill provides a curated, tested collection of the highest-value free public APIs organized by use case. Each entry includes the endpoint pattern, output shape, and curl example.

Philosophy: Curation + examples = the product. These are stable, mostly key-free APIs with good uptime.

Quick Reference

Category	API	No Key	CORS
Weather	wttr.in	✅	✅
Weather	Open-Meteo	✅	✅
Geocoding	ipapi (IP→location)	✅	❌
Geocoding	Nominatim (geocode)	✅	✅
Forex	open.er-api.org	✅	❌
Crypto	CoinGecko	✅	✅
Validation	urlmeta, icon.horse	✅	✅
Facts	catfact.ninja	✅	✅
Images	dog.ceo, thecatapi	✅	✅
Finance	Polygon.io	✅	✅
Reference	Wikipedia REST	✅	✅
Test data	jsonplaceholder, randomuser	✅	✅

---

Weather

wttr.in — Minimal Weather (CORS: ✅, No Key)

curl -s "wttr.in/San+Jose,CA?format=j1"

Use: Current conditions, 3-day forecast, moon phase, airport weather.

Output: JSON with

current_condition

,

weather[]

(daily),

nearest_area

.

# Specific location
curl -s "wttr.in/San+Jose,CA?format=3"
# Named locations work well; coordinates less so

---

Open-Meteo — Open Source Weather API (CORS: ✅, No Key)

Base:

https://api.open-meteo.com/v1/forecast

curl -s "https://api.open-meteo.com/v1/forecast?latitude=37.34&longitude=-121.89&current=temperature_2m,relative_humidity_2m,weather_code,wind_speed_10m&temperature_unit=fahrenheit&wind_speed_unit=mph&timezone=America%2FLos_Angeles"

Use: Current conditions + hourly forecast, no key needed, global coverage.

Parameters:

• latitude

  ,

  longitude

  — required

• current=

  — comma-separated variables:

  temperature_2m

  ,

  relative_humidity_2m

  ,

  weather_code

  ,

  wind_speed_10m

  ,

  precipitation

  ,

  cloud_cover

• hourly=

  — same variables for 48h forecast

• daily=

  — daily forecast:

  temperature_2m_max

  ,

  temperature_2m_min

  ,

  precipitation_sum

  ,

  weather_code

• temperature_unit=fahrenheit|celsius

• timezone=America%2FLos_Angeles

  (or auto)

Weather codes: 0=clear, 1-3=partly cloudy, 45-48=fog, 51-67=rain/drizzle, 71-77=snow, 80-82=rain showers, 95-99=thunderstorm.

---

Geocoding

ipapi.co — IP Geolocation (CORS: ❌, No Key)

Base:

https://ipapi.co/json/

or

https://ipapi.co/{IP}/json/

# Your sandbox出口IP
curl -s "https://ipapi.co/json/" | jq '.location, .city, .region, .country_name, .latitude, .longitude'
# Specific IP
curl -s "https://ipapi.co/8.8.8.8/json/" | jq '{city, region, country_name}'

Use: IP → city/region/country/lat-lon. Not CORS-friendly for browser use. Good for server/CLI agents.

Fields:

ip

,

city

,

region

,

region_code

,

country_name

,

country_code

,

latitude

,

longitude

,

timezone

,

utc_offset

,

asn

,

org

.

---

Nominatim — OpenStreetMap Geocoder (CORS: ✅, No Key, Rate Limited)

Base:

https://nominatim.openstreetmap.org/search

curl -s "https://nominatim.openstreetmap.org/search?q=1600+Amphitheatre+Parkway,+Mountain+View,+CA&format=json&limit=1&addressdetails=1" \
  -H "User-Agent: api-bridge/1.0"

Use: Address → lat/lon (forward) or lat/lon → address (reverse).

Reverse:

curl -s "https://nominatim.openstreetmap.org/reverse?lat=37.4223&lon=-122.0848&format=json" \
  -H "User-Agent: api-bridge/1.0"

Parameters:

• q=

  — search query

• format=json

  — always use this

• limit=1

  — first result

• addressdetails=1

  — include parsed address components

• accept-language=en

  — language preference

Rate limits: 1 req/sec. Always set

User-Agent

. Free for non-commercial use.

---

Forex

open.er-api.org — Free Forex (CORS: ❌, No Key)

Base:

https://open.er-api.com/v6/latest/{CURRENCY}

curl -s "https://open.er-api.com/v6/latest/USD" | jq '.rates | {JPY, EUR, GBP, CNY, CAD}'

Use: Current exchange rates. USD as base, all currencies relative to it.

Output:

{ "rates": { "JPY": 149.5, "EUR": 0.92, ... }, "time_last_update_utc": "..." }

---

Crypto

CoinGecko — Crypto Prices (CORS: ✅, No Key, Rate Limited)

Base:

https://api.coingecko.com/api/v3

# Simple price
curl -s "https://api.coingecko.com/api/v3/simple/price?ids=bitcoin,ethereum&vs_currencies=usd&include_24hr_change=true"

# Market data
curl -s "https://api.coingecko.com/api/v3/coins/markets?vs_currency=usd&ids=bitcoin,ethereum&order=market_cap_desc&per_page=5&sparkline=false&price_change_percentage=24h"

Rate limit: 10-30 calls/min on free tier. Cache responses when possible.

---

Validation

icon.horse — Favicon Checker (CORS: ✅, No Key)

Base:

https://icon.horse/

# Favicon URL for any domain
curl -s "https://icon.horse/feedburner.com"
# Returns: { "url": "https://feedburner.com/favicon.ico", "found": true }

Use: Find favicon for any domain — useful for link previews and metadata enrichment.

---

urlmeta — URL Metadata (CORS: ❌, No Key)

Base:

https://urlmeta.org/?

curl -s "https://urlmeta.org/?url=https://example.com"

Use: Get Open Graph / Twitter card metadata for any URL without scraping.

---

Facts

catfact.ninja — Cat Facts (CORS: ✅, No Key)

curl -s "https://catfact.ninja/fact"
# {"fact":"Cats have over 20 vocalizations...","length":42}

Use: Random fact generation for demos, tests, social content. Also:

/breeds

,

/fact

endpoints.

---

dog.ceo — Random Dog Images (CORS: ✅, No Key)

curl -s "https://dog.ceo/api/breeds/image/random"
# {"message":"https://.../images/n02102040_1005.jpg","status":"success"}

curl -s "https://dog.ceo/api/breeds/list/all" | jq '.message | keys'

Use: Random images for demos, placeholders, UI testing.

---

thecatapi — Random Cat Images (CORS: ✅, No Key)

curl -s "https://api.thecatapi.com/v1/images/search"
# [{"id":"d5D", "url":"https://...","width":1600,"height":1200}]

---

Finance

Polygon.io — Market Status & Stock Quotes (CORS: ❌, No Key)

Base:

https://api.polygon.io/v1

# Market status
curl -s "https://api.polygon.io/v1/marketstatus?apiKey=DEMO_KEY"

# Last trade for a stock  
curl -s "https://api.polygon.io/v2/aggs/ticker/AAPL/prev?adjusted=true&apiKey=DEMO_KEY"

Note:

DEMO_KEY

works for some endpoints. Real keys are free at polygon.io.

Also useful:

• https://api.polygon.io/v2/aggs/ticker/{TICKER}/prev

  — previous day close

• https://api.polygon.io/v2/aggs/ticker/{TICKER}/range?from={DATE}&to={DATE}

  — historical range

---

Reference

Wikipedia REST API — Article Summaries (CORS: ✅, No Key)

Base:

https://en.wikipedia.org/api/rest_v1

# Article summary
curl -s "https://en.wikipedia.org/api/rest_v1/page/summary/OpenAI" | jq '{title, extract, thumbnail}'

# Related pages
curl -s "https://en.wikipedia.org/api/rest_v1/page/related/OpenAI" | jq '.pages[:3] | .[].title'

Use: Factual summaries, links, thumbnails for topics. Good for enriching agent responses with context.

---

Test Data

jsonplaceholder — Fake JSON API (CORS: ✅, No Key)

Base:

https://jsonplaceholder.typicode.com

# Posts
curl -s "https://jsonplaceholder.typicode.com/posts?userId=1" | jq '.[0]'
# Comments
curl -s "https://jsonplaceholder.typicode.com/comments?postId=1" | jq '.[0]'
# Users
curl -s "https://jsonplaceholder.typicode.com/users/1" | jq '{name, email, phone}'
# Todos
curl -s "https://jsonplaceholder.typicode.com/todos?completed=false" | jq '.[0]'

Use: API prototyping, testing HTTP clients, mock backend during development.

---

randomuser.me — Fake User Profiles (CORS: ✅, No Key)

curl -s "https://randomuser.me/api/?results=3" | jq '.results[] | {name: .name, email, phone, location}'

Use: Generate realistic fake users with names, emails, photos, addresses for demos and tests.

---

Reliability Notes

✅ Reliable (tested, stable)

• wttr.in

  — always up, lightweight

• api.open-meteo.com

  — professional open source project, excellent uptime

• api.coingecko.com

  — large project, stable

• catfact.ninja

  — simple, reliable

• dog.ceo

  /

  thecatapi.com

  — pet image APIs, very stable

• jsonplaceholder.typicode.com

  — standard test API

• randomuser.me

  — standard test API

• en.wikipedia.org/api/rest_v1

  — Wikipedia infrastructure, very stable

⚠️ Use with caution

• nominatim.openstreetmap.org

  — rate limited to 1 req/sec, requires User-Agent

• open.er-api.org

  — simple project, less redundancy

• icon.horse

  — small project, less redundancy

• polygon.io

  — free tier sufficient for light use

❌ Avoid / Unreliable

• worldtimeapi.org

  — frequently down (2026-03 check failed)

• dog-api.kinduff.com

  — certificate expired, broken (2026-03 check failed)

---

Adding to an OpenClaw Skill

Install as a skill in your workspace skills directory:

# In your OpenClaw workspace:
ls skills/
# Add api-bridge/ subdirectory with this SKILL.md

The skill is documentation-first — no code to install. Agents read the SKILL.md and invoke the APIs directly.