BRREG MCP has well-structured tool definitions with clear naming (verb_noun pattern) and reasonable descriptions (avg 180 chars). All 6 tools have explicit input schemas with typed properties. However, parameter descriptions are sparse, many lack detail on format, constraints, or valid ranges. Output schemas are completely undocumented; LLMs cannot predict response structure. Error handling is minimal (generic HTTP errors only). No tool annotations (readOnlyHint, etc.). Composition is sound: tools are single-purpose and chainable via orgnr. Security is adequate (read-only API, no secrets in params). Naming is clear but could benefit from consistency (search_entities vs get_entity naming pattern is good, but no enum constraints on organisasjonsform or kommunenummer).

• Document output schemas for all tools. E.g., search_entities returns {_embedded: {enheter: [{orgnr, navn, organisasjonsform, naeringskode1, forretningsadresse, ...}]}, page: {totalElements, totalPages, ...}}. Include field types and descriptions.
• Add enum constraints to organisasjonsform (ASA, AS, ENK, etc.) and kommunenummer (0301, 0401, etc.) in search_entities and search_sub_entities. Replace free-form strings with validated enums.
• Enhance parameter descriptions with format/constraint details. E.g., 'size: number (1 - 10000, default 20)' and 'orgnr: string (exactly 9 digits, e.g. "923609016")'. Add regex pattern to schema if possible.
• Implement structured error handling. Catch HTTP errors and return actionable messages: 'Invalid org number format. Expected 9 digits, got "abc". Try search_entities() to find the correct orgnr.' Categorize as retryable (5xx) vs user-fixable (4xx).
• Add readOnlyHint: true to all tool schemas to signal safety to agents. Consider adding idempotentHint: true since all tools are GET-based and safe to retry.