letsfg 2026.5.83

Flight search & booking for AI agents. Server-side engine covers hundreds of airlines. Free search via Bearer token or prepaid Developer API.

LetsFG — Your AI agent just learned to book flights.

Server-side engine. Real prices. One function call. Search hundreds of airlines at raw airline prices — $20–$50 cheaper than Booking.com, Kayak, and other OTAs.

Two ways to use LetsFG

	CLI / SDK (PFS Bearer token)	Developer API
Search cost	Free (one-time letsfg auth, nothing charged)	Prepaid credits
Booking URL	1% fee (min $3) via letsfg.co	Direct airline URL, no fee
Speed	60–90 s	2–5 s (discover) · 60–90 s (full)
Setup	pip install letsfg && letsfg auth	letsfg.co/developers

Want direct airline URLs without any per-booking fee? Use the Developer API — prepaid credits, results in seconds, no per-booking fee.

Install

pip install letsfg

Authenticate once by putting a payment method on file (zero-amount, nothing charged), then search is free and unlimited:

letsfg auth           # one-time card-on-file setup → 90-day Bearer token (nothing charged)
letsfg search LHR BCN 2026-06-15

Search is free. Booking links require unlock (1% fee, min $3) — see Unlocking offer results below.

Authentication

from letsfg import LetsFG

# Register (one-time, no auth needed)
creds = LetsFG.register("my-agent", "[e-mail]")
print(creds["api_key"])  # "trav_xxxxx..." — save this

# Option A: Pass API key directly
bt = LetsFG(api_key="trav_...")

# Option B: Set LETSFG_API_KEY env var, then:
bt = LetsFG()

# Setup payment (required before unlock) — two options:

# Option 1: Stripe test token (for development)
bt.setup_payment(token="tok_visa")

# Option 2: Stripe PaymentMethod ID (from Stripe.js or Elements)
bt.setup_payment(payment_method_id="pm_1234567890")

The API accepts only Stripe-generated tokens or payment_method_id values — raw card numbers are not accepted.

The API key is sent as X-API-Key header on every request. The SDK handles this automatically.

Verify Your Credentials

# Check that auth + payment are working
profile = bt.me()
print(f"Agent: {profile['agent_name']}")
print(f"Payment: {profile.get('payment_status', 'not set up')}")
print(f"Searches: {profile.get('search_count', 0)}")

Auth Failure Recovery

from letsfg import LetsFG, AuthenticationError

try:
    bt = LetsFG(api_key="trav_...")
    flights = bt.search("LHR", "JFK", "2026-04-15")
except AuthenticationError:
    # Key invalid or expired — re-register to get a new one
    creds = LetsFG.register("my-agent", "[e-mail]")
    bt = LetsFG(api_key=creds["api_key"])
    bt.setup_payment(token="tok_visa")  # Re-attach payment on new key
    flights = bt.search("LHR", "JFK", "2026-04-15")

Quick Start (Python)

from letsfg import LetsFG

bt = LetsFG(api_key="trav_...")

# Search flights — FREE
flights = bt.search("GDN", "BER", "2026-03-03")
print(f"{flights.total_results} offers, cheapest: {flights.cheapest.summary()}")

# Unlock booking link (1% fee, min $3, charged via letsfg.co)
unlock = bt.unlock(flights.cheapest.id)
print(f"Confirmed price: {unlock.confirmed_currency} {unlock.confirmed_price}")

# Book — ticket price charged via Stripe (zero markup)
booking = bt.book(
    offer_id=flights.cheapest.id,
    passengers=[{
        "id": flights.passenger_ids[0],
        "given_name": "John",
        "family_name": "Doe",
        "born_on": "1990-01-15",
        "gender": "m",
        "title": "mr",
        "email": "[e-mail]",
    }],
    contact_email="[e-mail]"
)
print(f"PNR: {booking.booking_reference}")

Multi-Passenger Search

# 2 adults + 1 child, round-trip, premium economy
flights = bt.search(
    "LHR", "JFK", "2026-06-01",
    return_date="2026-06-15",
    adults=2,
    children=1,
    cabin_class="W",  # W=premium, M=economy, C=business, F=first
    sort="price",
)

# passenger_ids will be ["pas_0", "pas_1", "pas_2"]
print(f"Passenger IDs: {flights.passenger_ids}")

# Book with details for EACH passenger
booking = bt.book(
    offer_id=unlocked.offer_id,
    passengers=[
        {"id": "pas_0", "given_name": "John", "family_name": "Doe", "born_on": "1990-01-15", "gender": "m", "title": "mr"},
        {"id": "pas_1", "given_name": "Jane", "family_name": "Doe", "born_on": "1992-03-20", "gender": "f", "title": "ms"},
        {"id": "pas_2", "given_name": "Tom", "family_name": "Doe", "born_on": "2018-05-10", "gender": "m", "title": "mr"},
    ],
    contact_email="[e-mail]",
)

Resolve Locations

Always resolve city names to IATA codes before searching:

locations = bt.resolve_location("New York")
# [{"iata_code": "JFK", "name": "John F. Kennedy", "type": "airport", "city": "New York"}, ...]

# Use in search
flights = bt.search(locations[0]["iata_code"], "LAX", "2026-04-15")

Working with Search Results

flights = bt.search("LON", "BCN", "2026-04-01", return_date="2026-04-08", limit=50)

# Iterate all offers
for offer in flights.offers:
    print(f"{offer.owner_airline}: {offer.currency} {offer.price}")
    print(f"  Route: {offer.outbound.route_str}")
    print(f"  Duration: {offer.outbound.total_duration_seconds // 3600}h")
    print(f"  Stops: {offer.outbound.stopovers}")
    print(f"  Refundable: {offer.conditions.get('refund_before_departure', 'unknown')}")
    print(f"  Changeable: {offer.conditions.get('change_before_departure', 'unknown')}")

# Filter: direct flights only
direct = [o for o in flights.offers if o.outbound.stopovers == 0]

# Filter: specific airline
ba = [o for o in flights.offers if "British Airways" in o.airlines]

# Filter: refundable only
refundable = [o for o in flights.offers if o.conditions.get("refund_before_departure") == "allowed"]

# Sort by duration
by_duration = sorted(flights.offers, key=lambda o: o.outbound.total_duration_seconds)

# Cheapest offer
print(f"Best: {flights.cheapest.price} {flights.cheapest.currency}")

Error Handling

from letsfg import (
    LetsFG, LetsFGError,
    AuthenticationError, PaymentRequiredError, OfferExpiredError,
)

bt = LetsFG(api_key="trav_...")

# Handle invalid locations
try:
    flights = bt.search("INVALID", "JFK", "2026-04-15")
except LetsFGError as e:
    if e.status_code == 422:
        # Resolve the location first
        locations = bt.resolve_location("London")
        flights = bt.search(locations[0]["iata_code"], "JFK", "2026-04-15")

# Handle payment and expiry
try:
    unlocked = bt.unlock(offer_id)
except PaymentRequiredError:
    print("Run bt.setup_payment() first")
except OfferExpiredError:
    print("Offer expired — search again for fresh results")

# Handle booking failures
try:
    booking = bt.book(offer_id=unlocked.offer_id, passengers=[...], contact_email="...")
except OfferExpiredError:
    print("30-minute window expired — search and unlock again")
except AuthenticationError:
    print("Invalid API key")
except LetsFGError as e:
    print(f"API error ({e.status_code}): {e.message}")

Exception	HTTP Code	Cause
AuthenticationError	401	Missing or invalid API key
PaymentRequiredError	402	No payment method (call setup_payment())
OfferExpiredError	410	Offer no longer available
LetsFGError	any	Base class for all API errors

Timeout and Retry Pattern

Full cloud search takes 60–90 s (async polling). Use retry with backoff for transient errors:

import time
from letsfg import LetsFG, LetsFGError

bt = LetsFG()

def search_with_retry(origin, dest, date, max_retries=3):
    """Retry with exponential backoff on rate limit or timeout."""
    for attempt in range(max_retries):
        try:
            return bt.search(origin, dest, date)
        except LetsFGError as e:
            if "429" in str(e) or "rate limit" in str(e).lower():
                wait = 2 ** attempt  # 1s, 2s, 4s
                print(f"Rate limited, waiting {wait}s...")
                time.sleep(wait)
            elif "timeout" in str(e).lower() or "504" in str(e):
                print(f"Timeout, retrying ({attempt + 1}/{max_retries})...")
                time.sleep(1)
            else:
                raise
    raise LetsFGError("Max retries exceeded")

Rate Limits

Endpoint	Rate Limit	Typical Latency
Search	No hard limit (billing is the natural governor)	60–90 s
Resolve location	120 req/min	< 1 s
Unlock	20 req/min	2–5 s
Book	10 req/min	3–10 s

Minimizing Unlock Costs

Searching is free and unlimited, and so is booking on the PFS / CLI path (POST /api/agent-book, no LetsFG fee). The 1%-of-ticket unlock fee (min $3) exists only on the paid Developer API. Strategy:

# Search multiple dates (free) — compare before unlocking
dates = ["2026-04-01", "2026-04-02", "2026-04-03"]
best = None
for date in dates:
    result = bt.search("LON", "BCN", date)
    if result.offers and (best is None or result.cheapest.price < best[1].price):
        best = (date, result.cheapest)

# Unlock only the winner (1% fee, min $3)
if best:
    unlocked = bt.unlock(best[1].id)
    # Book within 30 minutes (ticket price only)
    booking = bt.book(offer_id=unlocked.offer_id, passengers=[...], contact_email="...")

Quick Start (CLI)

# Auth (one-time — saves Bearer token to ~/.letsfg/config.json)
letsfg auth

# Search (1 adult, one-way, economy — defaults)
letsfg search GDN BER 2026-03-03 --sort price

# Multi-passenger round trip
letsfg search LON BCN 2026-04-01 --return 2026-04-08 --adults 2 --children 1 --cabin M

# Business class, direct flights only
letsfg search JFK LHR 2026-05-01 --adults 3 --cabin C --max-stops 0

# Machine-readable output (for agents)
letsfg search LON BCN 2026-04-01 --json

# Unlock
letsfg unlock off_xxx

# Book
letsfg book off_xxx \
  --passenger '{"id":"pas_xxx","given_name":"John","family_name":"Doe","born_on":"1990-01-15","gender":"m","title":"mr","email":"[e-mail]"}' \
  --email [e-mail]

# Resolve location
letsfg locations "Berlin"

Search Flags

Flag	Short	Default	Description
--return	-r	(one-way)	Return date YYYY-MM-DD
--adults	-a	1	Adults (1–9)
--children		0	Children 2–11 years
--cabin	-c	(any)	M economy, W premium, C business, F first
--max-stops	-s	2	Max stopovers (0–4)
--currency		EUR	Currency code
--limit	-l	20	Max results (1–100)
--sort		price	price or duration
--json	-j		Raw JSON output

All CLI Commands

Command	Description	Cost
auth	One-time card-on-file setup → 90-day Bearer token. Nothing charged	FREE
search	Search flights between any two airports	FREE
locations	Resolve city name to IATA codes	FREE
unlock	[Developer API only] Unlock offer (confirms price, reveals booking URL)	1% of ticket, min $3
book	Book flight (creates real airline PNR)	Ticket price
register	Register new Developer API key	FREE
setup-payment	Attach payment card (required for unlock)	FREE
me	Show agent profile and usage stats	FREE

Every command supports --json for machine-readable output.

Environment Variables

Variable	Description
LETSFG_BEARER_TOKEN	PFS Bearer token (from letsfg auth). Takes priority over ~/.letsfg/config.json.
LETSFG_API_KEY	Developer API key (prepaid credits path)
LETSFG_BASE_URL	API URL override (default: https://letsfg.co)

How It Works

1. Search — Free. The server-side engine queries hundreds of airlines and returns real-time offers.
2. Book — Call POST /api/agent-book with your Bearer token. It returns either a confirmed order or a direct booking link for that exact offer, with no LetsFG fee either way.
3. Book — Open the direct airline URL and complete the booking on the airline's own site.

Prices are cheaper because we connect directly to airlines — no OTA markup.

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Also Available As

• MCP Server: npx letsfg-mcp — npm
• JS/TS SDK: npm install letsfg — npm
• Try without installing: letsfg.co — search instantly in your browser
• GitHub: LetsFG/LetsFG

⭐ Star the repo — we appreciate the support.

License

MIT