12 tools with mostly complete schemas and descriptions, but significant gaps in error handling, output documentation, and parameter clarity. Tool names follow verb_noun convention well (fat_zebra_*). Descriptions average ~120 chars, meeting baseline. However, 8 of 12 tools lack documented output schemas, making it unclear what fields agents should expect. Parameter descriptions are present but often generic ('optional' without explaining consequences). No error recovery guidance. Passthrough tool exposes security risks via flexible input. Missing idempotency hints on payment tools despite retry-prone operations.

• Document output schema for every tool. Example: fat_zebra_create_customer should return {customer_id: string, reference: string, created_at: ISO8601}. This enables agents to chain tools without guessing.
• Add idempotency hints to payment tools. Include 'idempotent: false' in descriptions and suggest reference-based deduplication: 'Use a unique reference per transaction to prevent duplicate charges on retry.'
• Tighten fat_zebra_passthrough validation: whitelist allowed endpoints (e.g., /purchases, /batches, /customers), reject unknown paths, cap request body size, and add rate limiting.
• Standardize date formats across all tools (use ISO 8601 YYYY-MM-DD everywhere, not YYYYMMDD). Document min/max for numeric params (e.g., limit: 1 - 100, amount: 1 - 999999999 cents).
• Add error recovery guidance to each tool. E.g., 'If batch not found, call fat_zebra_list_batches() with batch_type and status filters to locate it.' Return available alternatives in 404 responses.

Inferred effective spec: <=2025-11-25.

• Relies on Logging (deprecated) - log to stderr or use OpenTelemetry