This MCP server demonstrates solid fundamentals with 6 tools addressing CPF (Brazilian tax ID) validation and lookup. All tools have verb-noun naming, descriptions between 100-400 chars, and explicit input schemas with type definitions. Parameter descriptions are present and specific. However, output schemas are not formally documented, error handling lacks recovery guidance, and several parameters could benefit from stricter constraints (enums, ranges). The server correctly validates inputs early (CPF format/length checks in check_cpf), but error messages could be more actionable for LLM self-correction. Tool composition is sound, each tool has a single responsibility, and dependencies are well-documented (find_cpf_by_* require generate_valid_variations internally). The descriptions are LLM-friendly, explaining WHEN and WHY to call each tool.

• Add explicit output schemas to all tools. E.g., validate_cpf returns {valido: bool, cpf_formatado: string, error?: string}. Document these in the FastMCP response metadata or in tool descriptions.
• Enhance error responses with recovery hints. Example: check_cpf error 'CPF matematicamente inválido' should be: 'CPF is mathematically invalid. Try find_cpf_by_variations() to find the correct CPF if you have a partial or mis-typed version.'
• Add JSON Schema constraints (minimum, maximum, enum, pattern) to numeric and enum-like parameters. For workers: use integer with minimum=1, maximum=20. For mascara: use regex pattern matching valid wildcard positions.
• Clarify per-item error handling in check_multiple_cpfs description: 'Invalid CPFs are collected in the erros field; valid ones are consulted in parallel. The tool returns both successful matches and errors without stopping on first failure.'
• Provide English-language descriptions or glossary for domain terms. Add parentheticals: 'certidão (official record)', 'dígitos verificadores (check digits)', 'TRT3 (Brazilian labor court database)'.
• Document what fields are returned on success vs. error for each tool. E.g., check_cpf success returns {encontrado: bool, nome: string, data_nascimento: string, ...}, while error returns {erro: string}.
• Consider adding a 'confidence' or 'matches_count' field to find_cpf_by_* responses so the LLM knows whether the result is definitive or requires manual review.
• Add tool annotations (readOnlyHint=true) to all tools since none modify state, this helps clients optimize caching and parallelization.

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

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