{
  "success": true,
  "data": {"price": 42.50}
}

{
  "success": false,
  "message": "Invalid parameters"
}

# Register
curl -X POST https://api.fincept.in/user/register \
  -H "Content-Type: application/json" \
  -d '{"username": "john", "email": "john@example.com", "password": "Pass123!"}'

# After verification: credit_balance = 350

curl -X POST https://api.fincept.in/guest/create \
  -H "Content-Type: application/json" \
  -d '{"device_id": "test-device"}'

curl https://api.fincept.in/user/profile \
  -H "X-API-Key: fk_user_your_key"

{
  "success": true,
  "data": {
    "username": "johndoe",
    "credit_balance": 284.5,
    "account_type": "free"
  }
}

curl https://api.fincept.in/user/usage \
  -H "X-API-Key: fk_user_your_key"

{
  "success": true,
  "data": {
    "period": "last_30_days",
    "total_requests": 127,
    "total_credits_used": 65.5,
    "current_balance": 284.5,
    "endpoint_usage": {
      "/quantlib/pricing/black-scholes": {
        "count": 45,
        "credits": 90
      }
    }
  }
}

# Internal logic (for reference)
if user.credit_balance < required_credits:
    raise InsufficientCreditsError

# Atomic deduction with floor at 0
user.credit_balance = max(0, user.credit_balance - credits)

{
  "success": false,
  "message": "Insufficient credits",
  "detail": "Required: 5 credits, Available: 2 credits. Please purchase a new plan to continue."
}

Request A (5 credits) + Request B (5 credits) with balance = 7 credits

 Request A succeeds → Balance = 2
 Request B fails (insufficient) → Balance stays 2

Jan 1: +500 credits (subscription)
Jan 15: Used 200 credits → Balance = 300
Feb 1: Balance resets to 500 (Jan credits lost)

Active subscription: 500 credits/month
↓
Subscription expires
↓
Auto-downgrade to free tier: +350 credits (never expire)

curl -X POST https://api.fincept.in/cashfree/create-order \
  -H "X-API-Key: fk_user_your_key" \
  -H "Content-Type: application/json" \
  -d '{"plan_id": "credits_500"}'

curl -X POST https://api.fincept.in/cashfree/create-order \
  -H "X-API-Key: fk_user_your_key" \
  -H "Content-Type: application/json" \
  -d '{"plan_id": "basic_monthly"}'

# FREE - Check business day
POST /quantlib/core/date/is-business-day

# FREE - Parse date
POST /quantlib/core/date/parse

# 2 CREDITS - Price option
POST /quantlib/pricing/black-scholes

# Using Pro tier for simple mean
POST /quantlib/risk/var # Overkill!

# Using Basic tier
POST /quantlib/statistics/mean # Perfect!

5 separate calls × 2 credits = 10 credits

1 call with batch parameters × 2 credits = 2 credits

# Cache yield curve (2 credits once)
curve = api.build_curve(...)
cache.set("yield_curve_2024", curve, ttl=3600)

# Reuse for multiple bonds (0 extra credits)
for bond in bonds:
    price = api.price_bond(bond, curve=cached_curve)

curl https://api.fincept.in/user/transactions \
  -H "X-API-Key: fk_user_your_key"

{
  "success": true,
  "data": {
    "transactions": [
      {
        "id": 123,
        "transaction_id": "txn_abc123",
        "amount_inr": 4.99,
        "credits_purchased": 500,
        "status": "completed",
        "created_at": "2024-01-15T10:30:00Z"
      }
    ]
  }
}