documentation · v1

Siftfy docs

Updated May 12, 2026

Siftfy classifies arbitrary text and returns a calibrated spam probability from a single REST endpoint. Most integrations are two lines of code; the reference below covers everything beyond that.

Quickstart

Sign in, generate an API key from the dashboard, then POST text to /v1/predict:

curl
curl -sX POST https://api.siftfy.io/v1/predict \
  -H "X-API-Key: $SIFTFY_KEY" \
  -H "Content-Type: application/json" \
  -d '{"text": "Win a free iPhone! Click here NOW"}'

# {
#   "spam_probability": 0.65,
#   "likelihood": "medium",
#   "max_confidence": 0.84
# }

The response is a calibrated spam score between 0 and 1. Queue or soft-flag scores from 0.50 upward. Read the returned max_confidence before setting a block threshold: if the threshold is higher, the model alone cannot reach it. A score that has reached max_confidence is a lower bound rather than a probability, so compare against it instead of doing arithmetic with it — confidence ceiling explains why, and reading the score turns all of that into the four comparisons an integration actually makes.

Where to next

  • Authentication → how API keys work, where to put them, what 401 looks like.
  • POST /v1/predict → full request and response reference, including curl, Python, and JavaScript samples.
  • Reading the score → what each value means, the four bands, how to pick thresholds without hardcoding one, and two worked integration patterns.
  • POST /v1/feedback → report a ham or spam correction; the only route to a score you can act on automatically.
  • Content Gate (reCAPTCHA alternative) → zero-friction browser proof-of-work widget and siteverify API contract.
  • Errors → every status code we return and when each one fires.
  • Rate limits → per-tier quotas and the headers you can monitor to stay inside them.
  • SDKs → official Python client, plus what to do until other languages ship.
  • Changelog → model versions, API changes, and notable releases.

Plans & pricing

Free tier covers 10,000 requests per month at no cost; Pro is $9 plus $0.0001 per request after the included 1M. See pricing for the full breakdown, and rate limits for per-minute caps.