This Brevo MCP server has solid tool naming and comprehensive schema coverage, but descriptions are inconsistent in quality and some critical patterns are missing. All 15 tools are explicitly registered with input schemas in src/tools/definitions.js. Tool names follow verb_noun convention (get_, send_, create_, update_) which is strong. However, descriptions vary: some are clear and actionable (e.g., 'send_email': 'Send a transactional email using Brevo'), while others are generic (e.g., 'get_analytics_summary': 'Get comprehensive analytics summary with insights', lacks specificity on what 'comprehensive' means or when to use vs other analytics tools). Parameter schemas are well-defined with types, enums, and format constraints (email, pattern for dates), but parameter descriptions themselves are minimal and generic. No output schemas are documented, the tools return 'text' content without specifying structure, forcing LLMs to guess at response fields. Error handling exists in mcp-server.js (401, 429 status codes mapped to specific errors) but lacks recovery guidance. No tool annotations (readOnlyHint, destructiveHint, idempotentHint) are present despite clear read/write distinctions in the data. Security: API key is injected via BREVO_API_KEY env var (correct pattern), but no per-tool scope declarations exist.

• Add output schema documentation to every tool. Specify return type (object vs array), key fields, and types. Example for get_contacts: 'Returns: {type: "object", properties: {contacts: {type: "array", items: {type: "object", properties: {id: {type: "number"}, email: {type: "string"}, ...}}}, total: {type: "number"}}}'
• Rewrite tool descriptions to include WHAT (what data does it fetch/modify), WHEN (when should I use this vs similar tools), and OUTCOME (what can I do next with the result). Target 80-150 characters. Example: 'Get detailed open/click/bounce metrics for a specific campaign. Use this to analyze individual campaign performance; use get_campaigns_performance for batch metrics across multiple campaigns.'
• Add tool annotations. Mark send_email, create_email_campaign, send_campaign_now with {"destructiveHint": true}. Mark idempotent reads with {"readOnlyHint": true}.
• Enhance error messages in mcp-server.js. When status code is 401, return: 'Authentication failed. Your BREVO_API_KEY is invalid or expired. Regenerate it at https://app.brevo.com/settings/account and restart the server.' For 429: 'Rate limit exceeded. The Brevo API allows X requests per minute. Waiting Y seconds before retry...'
• Add permission declarations as a field in tool definitions. Example: {"name": "send_email", "permissions": ["send:email"]} and {"name": "create_email_campaign", "permissions": ["write:campaigns", "read:lists"]}.
• For destructive operations (send_campaign_now, update_campaign_status → sent/archive), add an optional 'dryRun' parameter (default false) that returns what would happen without committing. Or add a confirmation tool (e.g., confirm_send_campaign).