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 or pay per-request with crypto
• 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) or pay per-request with crypto (x402)
• 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

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

Who Pays What

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.

Crypto Payments (x402)

The x402 protocol enables account-free, per-request payments with stablecoins. This is designed for AI agents and programmatic clients that want to pay for API access without creating a Mu account.

How It Works

1. Client sends an API request without auth
2. Mu returns HTTP 402 Payment Required with an X-PAYMENT-REQUIRED header containing payment requirements (amount, network, asset, wallet address)
3. Client signs a payment on-chain (USDC on Base by default)
4. Client retries the request with the X-PAYMENT header containing the payment proof
5. Mu verifies the payment via a facilitator, settles on-chain, and serves the response

Configuration

Set X402_PAY_TO to enable:

# Required: your wallet address to receive payments
X402_PAY_TO="0xYourWalletAddress"

# Optional (defaults shown)
X402_FACILITATOR_URL="https://x402.org/facilitator"
X402_NETWORK="eip155:8453"                             # Base mainnet
X402_ASSET="0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913" # USDC on Base

Pricing

Credit costs are converted to USD at 1 credit = $0.01. For example, a web search (5 credits) costs $0.05 per request via x402.

x402 vs Stripe

Transfers

Users can transfer credits to other users on the network:

1. Go to /wallet/transfer
2. Enter the recipient’s username and amount
3. Credits are transferred instantly

Transfers are also available via the MCP wallet_transfer tool and the REST API.

Limits:

• Minimum: 1 credit
• Maximum: 50,000 credits (£500) per transfer
• Cannot transfer to yourself
• Sender must have sufficient balance

Transaction types:

• Transfers appear in both parties’ transaction history
• Sender sees a negative “transfer” transaction with the recipient’s ID
• Receiver sees a positive “transfer” transaction with the sender’s ID
• Transfers are instant and non-reversible

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

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

# x402 crypto payments (optional - set PAY_TO to enable)
X402_PAY_TO="0xYourWalletAddress"
X402_FACILITATOR_URL="https://x402.org/facilitator"
X402_NETWORK="eip155:8453"
X402_ASSET="0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"

# 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 for x402 payment header → verify and settle on-chain (no account needed)
3. Check if admin → allow (no charge)
4. Check daily free quota → allow if available, decrement
5. Check wallet balance → allow if sufficient, deduct credits
6. Otherwise → return 402 with payment requirements (if x402 enabled) or show “quota exceeded”

Security

• Full transaction audit trail
• Never allow negative balance