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

The annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description adds real context on top: the required 'listings:read' authorization and the fact that the response includes derived state such as what's left to make the listing complete and whether it can be submitted for review. It does not state what happens when the id is unknown or belongs to someone else, which is the main remaining behavioral gap.

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?

A single front-loaded sentence: identity and lookup key come first, the returned content second, the auth requirement last. The long parenthetical field enumeration is informative but heavy; trimming it to categories would read faster without losing much.

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 one-parameter, read-only lookup with an output schema and full annotation coverage, the description supplies everything needed to invoke it correctly: ownership scope, id requirement, auth scope, and payload contents. Only the not-found / not-owned failure mode is left unstated.

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% with a one-line description for productId, so the schema does most of the work. The description still adds a meaningful constraint by scoping the id domain to listings owned by the person you act for, which the schema's 'The listing's id.' does not convey.

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 opens with a precise verb and resource — 'One listing of the person you act for, by id' — which immediately separates it from list_my_listings (plural) and from get_product (an arbitrary product rather than one the acting user owns). It then enumerates exactly what comes back (editable fields, status, completeness gaps, review readiness), so an agent knows the payload shape before opening the schema.

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 clear context for use: fetching a single listing that belongs to the person you act for, gated by the 'listings:read' scope. It stops short of naming alternatives (e.g. use list_my_listings to discover ids, or get_listing_options for configuration choices), so there is no explicit when-not guidance.

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