The Mastercard Developers MCP server provides 9 well-structured tools for documentation and API discovery, but has moderate gaps in description quality and lacks output schema documentation. Tool naming follows verb_noun conventions (get-*, providing-, etc.), which is strong. All tools are READ_ONLY with proper risk classification. However, descriptions vary in quality, some are detailed (e.g., get-documentation-section-content: 169 chars with dependency hints), while others are minimal (e.g., get-services-list: 52 chars with no guidance on when to use it). Parameter schemas are present for most tools (7 of 9), but descriptions are sometimes generic. Tool 1 (get-services-list) has no visible input schema. No output schemas are documented in the source code, forcing LLMs to infer response structure. Error handling is basic, catch blocks return error messages as plain text without actionable recovery guidance or classification (retryable vs. user-fixable). Composition is solid: tools chain naturally (get-services-list → get-documentation → get-documentation-section-content → get-documentation-page), and outputs should carry IDs needed for downstream calls, though this is not explicitly verified in the source. Security is good: all tools are read-only, no secrets exposed as parameters. The server uses standard MCP SDK patterns and registers tools properly with descriptions and input schemas.

• Add output schema documentation for all tools. Example for 'get-services-list': 'Returns: {services: [{id: string, name: string, description: string, category: string}], total: number}'. This enables LLMs to plan downstream calls.
• Expand 'get-services-list' description to 150-250 chars, explaining purpose: 'Retrieve the list of all available Mastercard APIs and services. Use this first to discover available integrations (send, loyalty, locations, etc.) before calling get-documentation with a specific serviceId.'
• Add recovery guidance to error responses. Wrap execute() try-catch with error categorization: if (error.code === 'NOT_FOUND') return 'Service not found. Call get-services-list() to see available services.'; if (error.code === 'TIMEOUT') return 'Request timed out. Retry with smaller scope or check connectivity.'
• Document the parameter relationship between 'language' in OAuth guides. Add note: 'Language support varies by guide version. OAuth 1.0a supports: java, kotlin, c#, python, javascript, typescript, golang, others. OAuth 2.0 supports: java, kotlin, javascript, typescript, others.'
• Add minLength/maxLength and enum constraints to path-based parameters (pagePath, apiSpecificationPath). Current patterns are only regex-validated. Example: apiSpecificationPath must start with '/' and end with '.yaml' or '.json'.
• Clarify the difference between 'get-documentation-section-content' and 'get-documentation-page'. Current descriptions are similar; add: 'Section returns grouped pages with unified structure; Page returns single document. Use Section for overview, Page for deep dive.'