Server has 8 tools with complete Zod schemas and descriptions. Naming follows verb_noun convention (send_sms, get_balance, list_senders). Descriptions are present but brief (10-50 chars), below the 50-200 char LLM-optimized baseline. Parameters are typed and described, but lack constraints (enums, ranges, patterns). Output schemas are not documented, responses are raw JSON stringified without field documentation. Error handling is minimal; no recovery guidance or categorization. Security: credentials injected via environment variables (correct), but no permission gates or audit logging. Composition is reasonable, tools are single-purpose, but some lack chaining IDs (e.g., create_contact_group returns group_id but add_contacts requires it; unclear if returned). Missing idempotency hints and dry-run patterns for destructive operations (send_sms, send_bulk_sms).

• Expand tool descriptions to 50-200 chars. Example: 'send_sms: Send a single SMS message to a recipient. Requires pre-approved sender name. Returns message_id for tracking delivery status via get_sms_report. Charges 1 credit per SMS.'
• Document output schemas for each tool. Example: 'send_sms returns {message_id: string, status: string, cost: number, scheduled_at?: string}'. Include in tool description or separate schema block.
• Add parameter constraints: sender as enum (call list_senders first), page/per_page with min/max (1-100), schedule_at with ISO 8601 format hint, phone numbers with regex pattern (+<country><number>).
• Implement error recovery guidance in responses. Catch API errors and return: '{error: "Invalid phone number", hint: "Ensure format is +<country_code><number>, e.g. +905551234567", retryable: true}'.
• Add idempotency support: include idempotent_key parameter in send_sms/send_bulk_sms to prevent duplicate sends on retry. Document in description: 'Idempotent: same idempotent_key within 24h returns cached result.'