Critical gaps across all dimensions. Tool definitions are inferred from audit_vs_core.py and external plugin references rather than directly visible in source. No explicit schema definitions found in provided code. Descriptions are present but generic (10-50 chars, well below 50-200 char LLM-optimized baseline). Parameters lack type definitions and descriptions. No error handling guidance. No output schema documentation. This server wraps an external core plugin (mcp-einvoicing-core) but does not expose its own tool definitions clearly in the codebase provided.

• Provide complete server.py or main module showing explicit tool registration with FastMCP. Include full JSON Schema for each tool's input parameters with type, description, enum/pattern constraints, and required fields.
• Expand tool descriptions to 50-200 characters following LLM-optimized format: 'WHAT does it do? WHEN to use it? Any prerequisites?' Example: 'Create a ZUGFeRD 2.x invoice from structured data (company, items, totals). Use this to generate compliant German e-invoices before validation or transmission. Requires valid company tax ID and item details.'
• Add parameter descriptions for every input. Example: 'invoice_data (object): The invoice structure including company_name (string, required), items (array of {description, quantity, unit_price}), and totals (object with net_amount, tax_amount, gross_amount). All currency values in EUR cents.'
• For irreversible tools (peppol_send_invoice, invoice_create, datev_export), add error handling guidance: 'If transmission fails, check endpoint status with peppol_check_endpoint(). If validation fails, call invoice_validate() to see specific errors. Retryable errors: network timeout, endpoint unavailable. Non-retryable: invalid invoice structure, unsupported format.'
• Document output schemas for all tools. Example: 'Returns {invoice_id (string), validation_status (enum: valid|invalid|warnings), errors (array of {code, message, field}), zugferd_xml (base64-encoded XML), xrechnung_xml (base64-encoded XML)}. Use invoice_id for subsequent calls to peppol_send_invoice or datev_export.'

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

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