Summarize API: extractive text summarization for agents

Summarizes long text into a concise extractive summary using word-frequency sentence scoring, for $0.01 USDC per call through x402 on Base. No signup, no API key.

Endpoint

POST https://apisphere.us.ci/api/v1/summarize returns the top sentences from the input text, scored by word frequency. A plain GET only advertises the x402 payment challenge - send text over POST.

  • Price: $0.01 USDC per call, settled on Base through x402.
  • Max text length: 50,000 characters.
  • Default: returns 5 top sentences; configurable via max_sentences.

Request fields

Send a JSON body. Invalid bodies return 400 with field-level details.

  • text (required): 1 to 50,000 characters - the text to summarize.
  • max_sentences (optional): integer from 1 to 20, defaults to 5.
Paid request
curl -X POST https://apisphere.us.ci/api/v1/summarize   -H "Content-Type: application/json"   -H "X-PAYMENT: <signed-payment-payload>"   -d '{"text": "Long article text here...", "max_sentences": 3}'

Response

A 200 response returns the summary sentences, original and summary lengths, compression ratio, and the total sentence count, plus a meta block with the request id and latency.

  • 400 - invalid text or max_sentences (details in the response).
  • 402 - missing or invalid payment.
  • 429 - rate limited; honor Retry-After.
  • 500 - internal error; every response carries X-Request-Id for support.
Example 200 body
{
  "summary": [
    "Indonesia is an archipelago nation in Southeast Asia.",
    "It is the world's largest island country, with over 17,000 islands."
  ],
  "original_length": 320,
  "summary_length": 118,
  "compression_ratio": "63%",
  "sentence_count": 5,
  "meta": {
    "cache": "miss",
    "request_id": "7f3a9c2e-1b4d-4f6a-8c2e-9d1f5a3b7c4e",
    "latency_ms": 12
  }
}