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

Adds substantial behavior beyond the annotations: the logo kind replaces the existing logo, the image is fetched and validated server-side, live listings enter a review queue rather than applying immediately, and the call requires the listings:write scope. Annotations already cover the safety profile (readOnlyHint=false, destructiveHint=false), and the replacement note gives the nuance an agent needs; since the old image is only a logo, this does not contradict destructiveHint=false.

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 sentences, front-loaded with purpose, then the two behavioral facts that matter (validation and review queue), then the permission requirement. No restated title, no filler.

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 4-parameter mutation with an output schema and full annotation coverage, the description supplies the missing pieces: overwrite semantics, server-side fetching/validation, moderation delay on live listings, and the required scope. Nothing an agent needs to call this correctly is absent.

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?

With 100% schema description coverage the baseline is 3, but the description adds real meaning: it clarifies that kind=logo overwrites the previous logo (a semantic not stated in the schema's 'logo or photo'), and that the URL must be public and https. It says nothing extra about productId or alt, which the schema already covers.

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?

States a specific verb+resource (add an image to a listing) and splits the two modes explicitly: 'logo (kind logo, replaces the old one)' vs 'photo (kind photo)'. It also pins the source constraint to a public https image URL, so an agent can distinguish this from a direct-upload path.

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?

Usage is implied by the source constraint ('from a public https image URL') and the contrast with an upload, and the 'on a live listing it waits for review' clause hints at when the call is appropriate. However, it never names alternatives such as set_listing_cover or remove_listing_photo, nor states when not to use this tool (e.g., replacing a cover image).

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