Keywords L402 API

Extract keywords from any text passage.

50 sats per call, paid over the Lightning Network. No API key and no signup: the first request answers 402 Payment Required with a Lightning invoice, and repeating the request with the proof of payment returns your data.

l402_keywords 50 sats

Parameters

text Source text count Number of keywords

Call it with curl

The first call answers 402 with a Lightning invoice in the WWW-Authenticate header. Pay it from any Lightning wallet, then repeat the call with the L402 token and preimage.

cURL

curl -X POST https://lightningfaucet.com/api/ \
  -H "Content-Type: application/json" \
  -H "Authorization: L402 $MACAROON:$PREIMAGE" \
  -d '{"action":"l402_keywords","text":"Lightning channels route payments off-chain and settle in milliseconds.","count":5}'

What comes back

A successful call returns JSON, with the delivered content merged over the standard L402 receipt fields. Example values, not live data.

JSON

{
    "success": true,
    "http_code": 200,
    "service": "keywords",
    "timestamp": "2026-09-11T15:04:05+00:00",
    "paid_sats": 50,
    "keywords": [
        {
            "keyword": "Lightning channels",
            "relevance": 0.95
        },
        {
            "keyword": "off-chain payments",
            "relevance": 0.91
        },
        {
            "keyword": "routing",
            "relevance": 0.78
        },
        {
            "keyword": "settlement",
            "relevance": 0.74
        },
        {
            "keyword": "milliseconds",
            "relevance": 0.62
        }
    ],
    "text_length": 70,
    "count": 5
}

Call it from an AI agent

With lightning-wallet-mcp the payment is handled for you. From the CLI:

Terminal

lw pay-api "https://lightningfaucet.com/api/l402/keywords?text=Lightning+channels+route+payments+off-chain+and+settle+in+milliseconds.&count=5"

In Claude Code, Cursor or any MCP host, ask the agent to call pay_l402_api with that URL. The fee is 1% of the price, rounded down, so calls under 100 sats carry no platform fee.

Questions

How much does the Keywords API cost?
Each call costs 50 sats, paid as a Lightning invoice at request time. There is no subscription, no minimum and no monthly bill: you are charged for the calls you make.

Do I need an API key or an account?
No. Payment is the authentication. The first request answers 402 Payment Required with a Lightning invoice; settling it returns a preimage that authenticates the retry.

What does Keywords return?
A JSON object carrying keywords, text_length and count. See the example response above for the exact shape.

Related endpoints

Summarize 100 sats Sentiment 50 sats LLM Prompt 500 sats Ask a Human 500 sats Ask a Human: Result Free Bid Board 10-500 sats

All AI/LLM Utilities endpoints · How L402 authentication works · List your own API on the gateway