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.

• Pay as you go: Top up with a card or pay per-request with crypto
• Self-host: Run your own instance, no restrictions

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

Credit Costs

Note: Internal messages (user-to-user within Mu) are included at no cost. 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 usage — self-host. The code is open source (AGPL-3.0).

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 admin panel 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 per-request payments with stablecoins without needing a Mu account. This is designed for AI agents and programmatic clients that want to pay for API access directly.

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"`
}

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"

# Credit costs (optional - these are defaults)
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 wallet balance → allow if sufficient, deduct credits
5. Otherwise → return 402 with payment requirements (if x402 enabled) or show “credits required”

Security

• Full transaction audit trail
• Never allow negative balance