Wallet & Credits

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Wallet & Credits

Philosophy

Mu is a tool, not a destination. Like Google Search in 2000 — you arrive with intent, get what you need, and leave.

Credits are a straightforward way to pay for what you use. No dark patterns, no pressure to upgrade, no “unlimited” tiers that incentivize us to maximize your engagement.

  • Free tier: 10 AI queries/day - enough for casual utility use
  • Pay-as-you-go: Top up with a card, use credits when you need more
  • Self-host: Run your own instance for free, forever

We charge because LLMs and APIs cost money. Here’s our actual cost breakdown — we’re not extracting margin, just covering infrastructure.

How It Works

Credits

  • 1 credit = £0.01 GBP (1 penny)
  • Credits stored as integers to avoid floating-point issues
  • Top up via card payment (Stripe)
  • Credits never expire

Daily Free Quota

Every registered user gets 10 free AI queries per day:

  • Resets at midnight UTC
  • Covers news search, video search, and chat AI queries
  • No payment required

This should be enough if you’re using Mu as a utility. If you need more, pay-as-you-go.

Credit Costs

Feature Cost Why
News Search 1 credit (1p) Indexed search
News Summary 1 credit (1p) AI-generated summary
Video Search 2 credits (2p) YouTube API cost
Video Watch Free No value added over YouTube
Chat AI Query 3 credits (3p) LLM inference cost
Chat Room 1 credit (1p) Room creation
Places Search 5 credits (5p) Google Places API cost
Places Nearby 2 credits (2p) Google Places API cost
External Email 4 credits (4p) SMTP delivery cost
Weather Forecast 1 credit (1p) Weather API cost
Weather Pollen 1 credit (1p) Pollen data add-on

Note: Internal messages (user-to-user within Mu) are free. Only external email (to addresses outside Mu) costs credits.

Who Pays What

User Type Daily Free Credits Notes
Guest 0 N/A Must register
Registered 10 queries Pay-as-you-go When free quota exceeded
Admin Unlimited Not needed Site administrators

Why No “Unlimited” Tier?

Unlimited tiers create misaligned incentives. If you pay a flat fee for unlimited usage, we’re incentivized to make you use Mu more to feel you’re getting value. That’s the seed of engagement optimization.

Pay-as-you-go keeps us honest: we want to build efficient tools that solve your problem quickly, not sticky products that maximize your screen time.

If you want truly unlimited and free — self-host. The code is open source.

Card Deposits (Stripe)

When Stripe is configured (STRIPE_SECRET_KEY, STRIPE_PUBLISHABLE_KEY), users can top up with a credit or debit card:

  1. Go to /wallet/topup
  2. Enter any amount in whole pounds (e.g. £10), or use a quick-select preset (£5, £10, £25, £50)
  3. Complete payment via the Stripe Checkout page
  4. Credits are added automatically via the Stripe webhook (/wallet/stripe/webhook)

Rate: 1 credit = 1p — flat, no bonuses or tiers.

Configure a webhook in the Stripe Dashboard pointing to https://your-domain.com/wallet/stripe/webhook and set STRIPE_WEBHOOK_SECRET to the signing secret. The webhook listens for checkout.session.completed events.

Data Model

Wallet

type Wallet struct {
    UserID    string    `json:"user_id"`
    Balance   int       `json:"balance"`    // Credits (pennies)
    Currency  string    `json:"currency"`   // "GBP"
    UpdatedAt time.Time `json:"updated_at"`
}

Transaction

type Transaction struct {
    ID        string                 `json:"id"`
    UserID    string                 `json:"user_id"`
    Type      string                 `json:"type"`      // "topup", "spend", "refund"
    Amount    int                    `json:"amount"`    // Positive for topup, negative for spend
    Balance   int                    `json:"balance"`   // Balance after transaction
    Operation string                 `json:"operation"` // e.g., "news_search", "topup"
    Metadata  map[string]interface{} `json:"metadata"`
    CreatedAt time.Time              `json:"created_at"`
}

Daily Usage

type DailyUsage struct {
    UserID string `json:"user_id"`
    Date   string `json:"date"` // "2006-01-02"
    Used   int    `json:"used"` // Free quota used today
}

API Endpoints

Method Path Description
GET /wallet View balance and transaction history
GET /wallet/topup Show deposit address and instructions
POST /wallet/stripe/checkout Create a Stripe checkout session
GET /wallet/stripe/success Success page after Stripe payment
POST /wallet/stripe/webhook Stripe webhook for payment confirmation

Environment Variables

# Stripe card payments (optional)
STRIPE_SECRET_KEY="sk_live_..."
STRIPE_PUBLISHABLE_KEY="pk_live_..."
STRIPE_WEBHOOK_SECRET="whsec_..."  # For verifying Stripe webhook events

# Quota (optional - these are defaults)
FREE_DAILY_QUOTA="10"
CREDIT_COST_NEWS="1"
CREDIT_COST_NEWS_SUMMARY="1"
CREDIT_COST_VIDEO="2"
CREDIT_COST_VIDEO_WATCH="0"
CREDIT_COST_CHAT="3"
CREDIT_COST_EMAIL="4"
CREDIT_COST_PLACES_SEARCH="5"
CREDIT_COST_PLACES_NEARBY="2"
CREDIT_COST_WEATHER="1"
CREDIT_COST_WEATHER_POLLEN="1"

Implementation

Quota Check Flow

  1. User initiates search/chat
  2. Check if admin → allow (no charge)
  3. Check daily free quota → allow if available, decrement
  4. Check wallet balance → allow if sufficient, deduct credits
  5. Otherwise → show “quota exceeded” with options

Security

  • Full transaction audit trail
  • Never allow negative balance