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

Beyond the readOnly/idempotent/non-destructive annotations, it discloses cost (free, no account), output format and size (600 px WebP + markdown), that all stored views and paints are returned, and that no rendering or recoloring happens server-side. The 'Never renders' sentence is grammatically tangled ('...is an image from the account server'), which slightly blunts an otherwise strong disclosure.

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?

Front-loading 'Free, no account needed' is good, and little is pure filler. However the second sentence is an overstuffed colon construction that is hard to parse on first read, and parts duplicate the schema's parameter descriptions.

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?

For a read-only preview tool with full annotation coverage, a 100%-documented schema and an output schema, everything an agent needs is present: cost, output shape, fallback path with credit cost, id provenance, and how to present the result to the human.

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 coverage is 100%, so the descriptions of vehicle, view and color already carry the semantics, and the prose largely restates them (id format, view preference, no recoloring). It adds the useful routing hint that the id comes from resolve_vehicle/search_vehicles and tells the agent to report the actual view/color when it differs from the request, but that is marginal over the schema.

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 names a specific verb+resource (fetch the preview image already published for a catalog vehicle) and states the exact payload: a 600 px WebP, markdown, the view/paint it is in, and all stored views/paints. It also carves out what it is not ('Never renders') versus create_car_image_urls. The core statement is buried in clause-heavy prose, which keeps it just short of a 5.

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?

It gives explicit when-to-use (a vehicle with a picture already stored on its public page) and when-not (any other view, paint or size, or a vehicle with nothing stored – go to create_car_image_urls for 1 credit). It also tells the agent where the vehicle id comes from: resolve_vehicle or search_vehicles.

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