26 tools with consistent naming (verb_noun pattern: list_, get_, create_, update_, delete_) and basic descriptions. However, descriptions are uniformly terse (10-40 chars), falling below the 50-200 char LLM-optimized baseline. Input schemas are present for most tools but lack depth: parameter descriptions are minimal, no enums for constrained values (e.g., paymentMethod, status, events), no min/max bounds on numeric fields. Output schemas are not documented. Error handling is absent, no recovery guidance or actionable error messages. Security: API key injected server-side (good), but no permission gates on destructive tools (delete_webhook). Composition is sound, tools are single-responsibility and chainable (e.g., list_accounts → get_account → list_transactions). Overall: functional but underspecified for LLM reasoning.

• Expand all descriptions to 50-200 chars. Example: 'List all accounts' → 'List all Mercury accounts associated with your organization. Returns account IDs, names, and balances. Call this first to discover available accounts before querying transactions or cards.'
• Add enums to categorical parameters. For mercury_add_recipient, define paymentMethod as enum: ['domesticAch', 'wire', 'check']. For mercury_create_webhook, define events as enum: ['transaction.created', 'transaction.updated', 'invoice.sent', 'invoice.paid'].
• Document output schemas for all tools. Example for mercury_list_accounts: 'Returns {accounts: [{id: string, name: string, balance: number, currency: string}], total: number, nextCursor?: string}'. Include pagination fields (limit, offset, total) for list_* tools.
• Add parameter descriptions and constraints. For mercury_list_transactions, add: 'limit: Maximum number of transactions to return (1-100, default 20)'. For mercury_add_recipient, add: 'emails: Array of email addresses (at least one required, max 5).'
• Implement error recovery guidance. When a resource is not found, return available alternatives. Example: 'Account "acc_123" not found. Available accounts: acc_456 (Checking), acc_789 (Savings).' For write operations, add dry-run support or explicit confirmation before delete_webhook executes.