Six tools with basic schemas and descriptions, but significant gaps in parameter documentation and output schema clarity. Tool names lack action verbs (add, calculate, check_payment_history are acceptable but onetime_add, subscription_add, metered_add are vague about what distinguishes them). Descriptions are present but generic (10-50 chars for most). Input schemas show types but lack descriptions for most parameters. No documented output schemas. Error handling and recovery guidance absent. Composition issues: three tools (onetime_add, subscription_add, metered_add) appear to duplicate add functionality with payment gating, should be unified with a payment_tier parameter instead.

• Consolidate onetime_add, subscription_add, metered_add into a single 'add' tool with a required 'payment_tier' enum parameter (values: free, onetime, subscription, metered). Document what each tier requires (e.g., 'subscription requires active Stripe subscription').
• Document output schemas for all tools. E.g., add returns {result: number, timestamp: string}; check_payment_history returns {subscriptions: [{id, status, renewal_date}], one_time_purchases: [{id, date, amount}]}.
• Add descriptions to all parameters. For check_payment_history, document that it requires an authenticated user and returns payment history for the logged-in user's Stripe customer ID.
• Add error handling guidance to tool descriptions. E.g., 'If payment fails, the error will indicate whether the card was declined, subscription expired, or metered limit exceeded. Retry is safe for declined cards; ask user to renew subscription if expired.'
• Add dependency hints to tool descriptions. E.g., 'Call check_payment_history first to verify the user has an active subscription before calling subscription_add.'