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

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.