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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds a genuinely new behavioral fact not in annotations — no API key and no cost — but says nothing about pagination, error behavior for a bad ID, or what "in full" includes.

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?

Two short fragments with zero filler and the key fact front-loaded, which is good. However, the brevity is achieved by omitting required information rather than by tight editing, so it reads as under-specified rather than efficient.

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 lookup tool with a required identifier, no output schema, and no parameter documentation, the description leaves the agent without the ID format or any sense of the returned shape. Annotations cover safety, but the operational essentials are missing.

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 0% for the single required listing_id, so the description must carry the burden and does not: no ID format, no example, no indication of where the ID comes from (e.g., search_listings). Only the implicit notion that one listing is addressed adds anything.

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?

"One listing in full" conveys the resource (a single listing) and the scope (full detail, as opposed to a summary list), which loosely separates it from search_listings and my_listings. But there is no verb and no explicit statement that it retrieves a listing by ID, so an agent has to infer the operation.

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?

There is no when-to-use guidance, no mention of prerequisites, and no routing to siblings such as search_listings (find an ID) or get_shop (related entity). "Free, no key" describes access terms, not usage conditions.

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