Vensim MCP has 7 tools with basic descriptions and minimal parameter documentation. All tools have descriptions (10-100 chars), but most are terse and lack actionable context for LLM selection. Input schemas are present but sparse: most parameters lack type constraints, enums, or format guidance. No output schemas are documented. Error handling is absent, tools return raw dict responses with no recovery guidance. Tool names follow verb_noun convention (good), but descriptions do not explain WHEN to use each tool or what prerequisites exist. No tool annotations (readOnlyHint, destructiveHint, idempotentHint) despite clear risk profiles (WRITE, IRREVERSIBLE operations). Parameter descriptions are minimal or missing entirely.

• Add output schemas to all tools. Document return types as JSON Schema: e.g. generate_vensim_model returns {model: string (file path), validation: {ok: boolean, errors: string[]}}. This enables LLMs to chain tools and extract required IDs.
• Expand parameter descriptions to 50-150 chars with format/constraint guidance. E.g. 'spec_json: JSON string (UTF-8) containing a model specification object with required keys: variables (array), equations (object), views (array). Example: {"variables": [{"name": "Stock", "unit": "units"}], ...}'
• Add tool annotations via FastMCP. Mark generate_vensim_model, render_vensim_preview, create_vensim_dss_script with destructiveHint=true (they write files). Mark open_vensim_model with destructiveHint=true (launches external app). Mark vensim_doctor, inspect_vensim_model, validate_vensim_model with readOnlyHint=true.
• Implement structured error responses. Catch exceptions and return {ok: false, error: 'Invalid JSON in spec_json', details: 'Expected object with keys: variables, equations, views', recovery: 'Validate JSON syntax and required fields'}. Include actionable next steps.
• Add parameter constraints. Specify output_path must be absolute or relative to cwd, directory must exist or be created, file extension must match (.mdl, .svg, .cmd). Add run_name length limit (1-50 chars, alphanumeric + underscore). Use JSON Schema minLength, maxLength, pattern properties.