MCP Carvana

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden of behavioral disclosure. It mentions checking availability and getting estimates/fees, but it does not disclose critical behavioral traits such as whether this is a read-only operation, if it requires authentication, potential rate limits, or what happens if the zip code is invalid. For a tool with no annotation coverage, this leaves significant gaps in understanding its operational context.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, well-structured sentence that efficiently conveys the tool's purpose, scope, and outputs without any wasted words. It is front-loaded with the core action and resource, making it easy to understand at a glance, and every part of the sentence contributes essential information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's moderate complexity (2 parameters, no output schema, no annotations), the description is adequate but incomplete. It covers the basic purpose and parameters but lacks details on behavioral aspects like error handling, response format, or integration with sibling tools. Without annotations or an output schema, more context on what to expect from the tool would improve completeness.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, with clear descriptions for both parameters ('zip_code' and 'stock_number'). The description adds marginal value by implying that 'zip_code' is the primary input for delivery checking and 'stock_number' is optional for vehicle-specific queries, but it doesn't provide additional semantics beyond what the schema already documents, such as format constraints or examples.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the specific action ('Check whether Carvana can deliver'), the resource ('a vehicle'), and the scope ('to a specific zip code'), with additional details about what information is returned ('estimated delivery timeframe and any associated fees'). It distinguishes this tool from siblings like 'find_nearby_vending_machines' or 'get_vehicle_details' by focusing on delivery logistics rather than vehicle comparison, location search, or data retrieval.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage when delivery feasibility is needed, but it does not explicitly state when to use this tool versus alternatives or provide any exclusions. For example, it doesn't clarify if this should be used before or after selecting a vehicle, or if it's only for purchased vehicles versus general inquiries. The context is clear but lacks explicit guidance on alternatives or prerequisites.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.