open-esg-korea is a well-structured Korean ESG data server with 15 tools covering company lookup, ratings, governance, and emissions. Strengths: consistent verb-noun naming (company, ratings, ghg_emissions), resource-rich descriptions in Korean with clear purpose statements, proper input schemas with type declarations and descriptions. Weaknesses: no tool annotations (readOnlyHint/destructiveHint/idempotentHint) despite all tools being READ_ONLY; output schemas not documented in code; no structured error handling guidance; parameter descriptions lack detailed format/constraint specifications (e.g., 'isu_cd' says '6자리 종목코드' but no validation examples). Tool descriptions average ~120 chars (Korean), above the 10 - 1024 baseline and generally actionable. All 15 tools have parameter schemas with type + description, meeting the critical minimum. Composition is clean, each tool has single responsibility. However, no confirmation steps for multi-resource queries, and some parameter relationships (e.g., from_year/to_year defaults) lack explicit documentation of edge cases.

• Add tool annotations to all 15 tools: readOnlyHint=true for all (no state mutation). Enables LLM to infer idempotency and safe retry logic.
• Document output schemas for each tool. Example for 'ratings': return type = {isu_cd: string, year: integer, ratings: {agency: string, grade: string, status: string}, warnings: [string]}. Helps LLM plan downstream calls.
• Enhance parameter descriptions with format rules and examples. E.g., isu_cd: '6-digit KRX ticker code (e.g., 005930 for Samsung). Must be numeric. Non-existent codes return empty ratings.'
• Add pagination guidance to 'company_list' and 'report_list'. Specify: max results per call, how to iterate (offset-based or cursor-based), and total count field in response.
• Document default year/date behavior explicitly. E.g., 'report_list' from_year/to_year: 'Defaults to last 5 years. If company founded after from_year, returns records from founding year onward.'
• Add recovery paths in descriptions. E.g., 'company': 'If search returns no results, try: (1) partial name match via company_list; (2) direct 6-digit ticker if known; (3) DART corporate code lookup.'
• Include relationship hints between tools. E.g., 'company' description: 'Use this first to resolve company name to isu_cd, then pass isu_cd to ratings, ghg_emissions, etc.'
• Validate and fail fast for invalid isu_cd format. Return actionable error: 'Invalid isu_cd: got "12345" (5 digits). Must be 6-digit numeric code. Example: 005930.'
• For report text tools (sustainability_report, gov_report), document acpt_no format and provide example of how to obtain it from report_list response.