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

Annotations already declare not-read-only, open-world, non-idempotent, non-destructive, but the description adds the key behavioral fact that a photo price 'runs a real scan on their account' and requires sign-in, plus the currency/marketplace scoping (eBay US USD vs price.currency). This explains the non-read-only, open-world hints with concrete consequences.

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-loaded with what the tool returns, but it is one long clause-stacked paragraph with four parenthetical asides and no visual structure, making it dense to parse. Every element is relevant, yet the absence of structure costs it.

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?

With no output schema, the description carries the full burden and does so: it enumerates the returned fields (estimate, range, comps with links, three list prices with sell chance, net proceeds, verdict), states currency scope, and covers the sign-in requirement for photo scans. An agent has what it needs to call and interpret it.

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 baseline is 3, but the description adds meaning beyond the schema: it ties cost to the worth-it verdict, explains currency depends on whether the call is a description price (USD) or a signed-in photo scan (seller's currency), and reinforces image_url as preferred over description.

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 (price) and resource (secondhand item on eBay) and enumerates the returned artifacts: estimate with range, sold comps, three list prices with 14-day sell chance, seller net after fees, and a worth-it verdict. It clearly implies overlap with siblings like get_sold_comps and worth_it but never names them to route the agent, so it stops short of sibling differentiation.

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 a real conditional: use image_url (needs sign-in through the connector, priced in the user's own marketplace/currency) versus falling back to a text description when not signed in, and notes a photo reads better. It stops short of routing among siblings such as get_sold_comps or worth_it, so no explicit when-not statement.

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