Server has 6 well-named tools with complete input schemas and descriptions. All tools follow verb_noun naming (altos_*) and are READ_ONLY. Descriptions are clear and domain-specific (10 - 150 chars, within baseline). However, output schemas are completely undocumented, the code returns parsed CSV data or JSON but never specifies what fields agents should expect. Parameters lack enums for constrained values (e.g., res_type, quartile, type should be enums). No error handling guidance, no pagination documentation despite tools returning lists. API key exposure via _altosKey parameter violates secret-injection pattern. Missing per-parameter type constraints (e.g., weeks max 52 is stated in description but not enforced in schema).

• Document output schemas for all tools. Specify the structure of returned objects (e.g., altos_market_stats returns {inventory: number, new_listings: number, median_price: number, days_on_market: number, market_action_index: number}). This enables agents to plan downstream calls.
• Move API key to server-side secret injection. Remove _altosKey parameter and inject the key from an environment variable (ALTOS_API_KEY) or vault. Update documentation to explain how to configure the key at server startup.
• Convert constrained parameters to enums. Change res_type, quartile, and type from free-form strings to JSON Schema enum arrays. Example: 'res_type': {type: 'string', enum: ['single_family', 'multi_family'], description: '...'}.
• Add pagination and result-limit guidance. Document that limit defaults to 100 and caps at 1000. For tools returning lists, specify whether results are sorted, whether a total_count is returned, and how to fetch the next page.
• Implement error classification and recovery hints. Catch API errors and return structured responses like {error: 'invalid_region', message: 'Region code not found', suggestion: 'Try us_national or ca_los-angeles'}. Distinguish retryable (network timeout) from user-fixable (invalid region) errors.