VGP server has clear, well-documented tool definitions with strong descriptions (avg 150 chars) and complete input schemas. All 4 tools are read-only and properly annotated. However, output schemas are not formally documented in the code, and parameter descriptions lack detail on constraints and error cases. Tools follow a coherent naming pattern (giving_*) but lack verb-first convention. No error handling guidance or recovery paths documented.

• Add formal output schemas to each tool registration. Document giving_verify returns {legal_name: string, display_name: string, ein: string, canonical_domain: string, vgp_version: string, approved: boolean, last_updated: string}. Document giving_options returns array of {id, method, provider, authorized_url, recipient, recurring, restrictions, designation_support}. Document giving_designations returns array of designation objects with id, name, description fields.
• Enhance parameter descriptions with constraint details. For 'amount': 'Donation amount in the site's displayed currency (USD, EUR, etc.). Must be > 0 and ≤ 1,000,000. Platforms may round to nearest cent.' For 'frequency': 'Giving frequency (e.g. one_time, monthly, annual). Valid values depend on the destination, call giving_options first to see destination.prefill.parameters.frequency.values.'
• Add structured error responses. Instead of throw new Error('VGP has no authorized destinations'), return {error: 'no_authorized_destinations', message: 'This nonprofit has not configured any authorized donation destinations. Contact the organization to set up VGP.', retryable: false}. Guide LLM on next steps.
• Rename tools to verb_noun convention: giving_verify → get_giving_verification, giving_options → list_giving_destinations, giving_designations → list_giving_designations, giving_prepare → prepare_giving_url. Improves LLM intent inference.
• Document the 'rejected' field in giving_prepare response. Explain that rejected is an array of parameter names that were not applied (e.g. ['frequency', 'cross_origin_template']) and why. Add guidance: 'If critical parameters are rejected, call giving_options to verify the destination supports them.'