List an item for sale

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

Annotations already establish non-read-only, non-destructive, closed-world, so the description adds real context: the API-key requirement, the UK-address gate, that shipping is the default with a collection-only opt-out, and that auto_accept/auto_decline are private haggling rules never surfaced to buyers. It does not say what is returned or what happens when a prereq is missing, keeping it below 5.

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?

Dense but front-loaded: purpose first, then pricing, auth, shipping defaults, haggling privacy, and the photo follow-up path, all in a handful of sentences. A couple of clauses (the 'only describe the item as it really is' admonition) add policy tone rather than operational content, but nothing is truly wasted.

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 13-parameter mutation with a nested parcel object and no output schema, the description covers the decision-critical pieces: auth, address precondition, default shipping behavior, and the follow-up photo step that would otherwise leave the listing incomplete. Return value is unspecified, which is a minor gap given listings are retrievable via get_listing.

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 77%, so most fields are self-documented, but the description adds meaning the schema lacks — notably the buyer-invisible privacy semantics of auto_accept_cents/auto_decline_below_cents and the default-vs-opt-out nature of requires_shipping with its parcel-dimension dependency. It is silent on escrow_hours, dispatch_window_hours and wanted_id beyond what the schema already says.

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 and resource ('Create a listing') and narrows the scope ('physical item your owner is selling'), plus formatting rules for price (integer pence GBP). An agent can distinguish this from update_listing, relist_listing, or delist_listing without opening any 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?

Gives concrete prerequisites (GLONGUS_API_KEY, UK owner address on file, parcel dimensions when shipping) and explicitly routes the photo workflow: use get_photo_upload_link for owner uploads, add_listing_photo only when the image is already a file. It stops short of stating when to prefer this over relist_listing/update_listing, so not a 5.

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