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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety and external reach are covered. The description adds specificity about breadth (naming eBay, Fanatics Collect, Pristine Auction, Goldin, CardHobby, Memory Lane) and that results are live listings, but discloses no pagination behavior, rate limits, or auth requirements beyond the schema.

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 beginning with the verb, with the source enumeration set off by dashes. It is dense but not padded; the parenthetical list is informative rather than filler, though the sentence is long enough to be slightly unwieldy.

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?

An output schema exists, so return values need no explanation, and all 8 parameters are fully covered by the schema. The description conveys purpose, scope, and filterable dimensions, leaving only explicit sibling routing as a gap.

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%, so every parameter is already documented, including defaults for q, page, per_page and the alt-categories-sourced lists for sort/category/listing_type/auction_house/grading_company. The description merely restates the filter dimensions without adding syntax or semantics beyond the schema, so the baseline 3 applies.

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 (search) and resource (Alt's universal aggregator index of live auction and fixed-price listings), and enumerates the sources and filterable dimensions. It clearly distinguishes itself from siblings like alt_sold_listings (sold) and alt_card_search by emphasizing the cross-auction-house live-listing scope.

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?

The scope description implies when it applies (aggregated live listings across external houses), which lets an agent infer it is the broad search entry point. However, it never names alternatives such as alt_card_search, alt_sold_listings, or alt_auctions, nor states when not to use it. Usage is implied rather than explicit.

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