API Reference

The Fía Rent API returns an estimated fair monthly rent for any US address — blending Census median rent with Fía comparables, plus an AI market read on paid plans.

Base URL & authentication

Base URL https://fia.rent. Every request needs your key in the x-api-key header — create one at /developers/keys.

Keys & quota

• Your monthly quota belongs to your account and is shared across all your keys.
• Create multiple keys (dev / prod / rotation) — they're just credentials and don't add quota.
• Subscribe once to activate your account; every key works immediately.
• Create keys, revoke them, watch usage, and cancel anytime at /developers/keys.
• To rotate: create a new key, switch your app to it, then revoke the old one.

Endpoint

GET /api/v1/rent-estimate

Parameters

address	string — full street address (geocoded). Provide this, or zip, or lat+lon.
zip	string — 5-digit ZIP code.
lat, lon	number — coordinates.
bedrooms	integer — 0–4+. Default 2.

Example

Request

curl "https://fia.rent/api/v1/rent-estimate\
  ?address=1524+S+6th+St+Milwaukee+WI&bedrooms=2" \
  -H "x-api-key: fia_live_..."

Response

{
  "query": { "zip": "53204", "bedrooms": 2, "lat": 43.01, "lon": -87.92 },
  "estimate": 985,
  "currency": "USD",
  "low": 887,
  "high": 1084,
  "method": "ai_grounded",
  "tier": "pro",
  "sources": { "census_baseline": 950, "comparables": 4 },
  "insight": "Con base en la mediana del Censo ($950) y 4 comparables
    en Fía, ~$985/mes es razonable para 2 recámaras. Es una estimación.",
  "provider": "Fía · Wellness Labs LLC",
  "disclaimer": "Estimación informativa. No es un avalúo."
}

Response fields

estimate	Estimated fair monthly rent (USD), or null if there isn't enough data.
low / high	Confidence range around the estimate.
method	How it was derived (see below).
sources	census_baseline value + count of Fía comparables used.
insight	AI market rationale — Pro & Business plans only.
tier	Your plan (free / pro / business).

Method values

census_baseline	Census median gross rent for the area.
comps	Fía comparable listings in the area.
blended	Average of the Census baseline and comparables.
ai_grounded	AI-refined estimate reasoned over the real data (Pro+).
insufficient_data	No baseline or comparables — estimate is null.

Errors

400	Missing address, zip, or lat+lon.
401	Missing or invalid API key.
429	Rate limit (30/60s) or monthly quota exceeded.

Rate limits & plans

• 30 requests / 60s per key and per IP.
• Monthly quota — Standard 10,000 · Business custom, shared across all keys on your account. All plans are paid (no free tier).
• The AI insight is included on all paid plans.

Estimates are informational, not appraisals. Fía Rent API · a service of Wellness Labs LLC.