This server has 45 tools with significant structural gaps. Most tools lack detailed parameter descriptions, many parameters are described only as 'object' with no field-level documentation. Tool descriptions are present but generic (avg ~60 chars, well below the 194-char baseline). No output schemas are documented. The generic 'call_api' tool (tool #45) is a red flag: it bypasses the entire tool abstraction layer and exposes raw API complexity to the LLM. Parameter validation is minimal; many tools accept opaque 'body' objects without schema constraints. Error handling is absent, no recovery guidance, no categorization of retryable vs fatal errors. Security: credentials are injected via environment variables (good), but no per-tool permission gates or audit logging visible. Composition is weak: tools like 'create_invoice', 'cancel_invoice', 'remove_invoice', 'finalize_invoice' are similar enough to cause LLM confusion. No pagination support visible despite financial data that could return large result sets.

• Remove or deprecate 'call_api' tool. Replace with explicit, well-defined tools for each API endpoint. If new endpoints are needed, add them as proper tools rather than exposing raw HTTP.
• For all 'body' parameters, expand to explicit field-level schemas. E.g., create_invoice body should list required fields (amount, currency, description) with types and constraints.
• Document output schemas for all tools. Include field names, types, and which fields are needed for downstream tool calls (e.g., invoice_id from create_invoice is input to get_invoice_status).
• Add error handling: wrap API calls in try-catch, categorize errors (retryable, user-fixable, fatal), and return actionable messages. E.g., 'Invalid IBAN format. Expected 28 chars, got 20. Example: UA213223130000026007233566001'.
• Consolidate similar invoice tools: clarify the semantic difference between cancel (reversible) and remove (destructive). Add descriptions explaining when each is appropriate. Consider renaming remove_invoice to delete_invoice for clarity.