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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety and open-world profile is covered without description help. The description adds limited behavioral context beyond naming the two market segments (auctions and fixed-price). It does not mention pagination defaults, result caps, or currency quirks, but the schema and output schema absorb much of that.

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 the purpose followed immediately by the routing guidance. No filler or restatement of the name.

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 22-parameter read-only search tool with an output schema and full schema coverage, the description supplies purpose and sibling routing and relies on structured fields for the rest. It is essentially complete, with only minor missing behavioral notes about pagination or result limits that the schema largely addresses.

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%, with all 22 parameters documented in the schema itself, so the schema does the heavy lifting. The description only names broad filter categories that map onto parameters already explained in detail (e.g. brand, seller_id, auction_urn). Baseline 3 is appropriate.

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 ("Search Fanatics Collect's auctions and fixed-price marketplace") and enumerates the filter dimensions (query, category, grading, price, year, listing filters). It also names the sibling tools it is not, so an agent can separate it from fanaticscollect_listing, fanaticscollect_auctions, and fanaticscollect_sold_items 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?

Explicitly routes the agent: fanaticscollect_listing for one listing, fanaticscollect_auctions for auctions, fanaticscollect_sold_items for completed sales. The when-to-use-which-tool decision is stated rather than inferred. The only minor wrinkle is that search itself covers auctions, but the sibling routing is clear.

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