Single tool 'buy_spot_check' with well-structured definition. Tool name is action-verb-based and clear. Input schema present with all three parameters typed as strings and described. Description explains purpose (purchasing certificate with specific data) but could be more LLM-optimized regarding when/why to call it. No output schema documented, critical gap. Error handling not visible in definition. Risk classification (READ_ONLY) present and appropriate, suggesting some security awareness.

• Document the complete output schema for buy_spot_check response. Include all fields returned (e.g., certificate_id, rounds_recorded, verdicts_count, observation_dates, coverage_percent, gaps_list, badge_url) with types and descriptions so the LLM knows what data is available.
• Expand the tool description to ~150-200 characters explaining: (1) purpose, purchasing a conformance certificate for a specific host; (2) when to use, when the agent needs to generate official evidence of x402 readiness for audit/compliance; (3) what comes back, a signed certificate with specific attestations the LLM can present to users.
• Add maxLength: 80 constraint to agent_name schema and maxLength: 280 to purpose schema instead of relying on prose-only descriptions.
• Add format constraint to 'host' parameter. Either 'hostname' format in JSON Schema or explicit description: 'A bare hostname without protocol or path (e.g., example.com, not https://example.com/path).'
• Include error guidance in the tool description or a separate errors section: 'May fail if: host is invalid/unreachable (suggest verify with DNS lookup first), agent_name exceeds 80 chars, purpose exceeds 280 chars, payment processing fails (user should confirm balance/API key).'
• Consider adding a dry_run parameter (boolean, default false) if the operation is costly. This follows the confirmation-request pattern and prevents accidental certificate purchases during agent exploration.