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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description adds real value beyond that: it discloses the stub status, the auth requirement ('Requires an Attic API key'), and the fact that no comp data is returned — all things the annotations cannot convey.

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?

Four short sentences, front-loaded with the critical 'STUB' warning so the agent sees it first. There is mild overlap between 'Does not return eBay sold prices' and 'Do not call this to price a card', but every sentence carries distinct information.

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 stub with no output schema and full annotation coverage, the description supplies the essential facts an agent needs: it is non-functional, it needs an API key, and it must not be used to price cards. The only gap is not routing the agent to the sibling that would actually serve the request.

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 description coverage is 100% and the schema itself already repeats the stub caveat for the q parameter, so the description adds no parameter-level meaning. The baseline of 3 is appropriate when the schema carries the full parameter burden.

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 states plainly that this is a STUB and does not return eBay sold prices for sports cards, which prevents the agent from mistaking it for a functional comps tool. It also disambiguates from the adjacent PCGS/coin territory. However, it never states positively what the tool does return when called, only what it does not.

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 an explicit when-not-to-use rule ('Do not call this to price a card') and a prohibition against fabricating output ('do not invent a hammer or a sold comp'), which is unusually strong guidance. It stops short of naming the correct alternative, such as attic_comps_status or attic_coin_sold_comps.

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