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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), yet the description still adds material context: public/no sign-in, no stock reservation or price-change side effects, and distinct failure semantics for unknown products (no-match message) versus malformed input (tool error). It also discloses that out-of-stock products omit prices, which would otherwise be mistaken for a bug.

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?

Purpose, then usage and exclusions, then return payload, then auth/safety, then failure modes — a deliberate front-to-back order with no filler sentences. Each clause carries distinct information an agent needs at call time.

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 burden of describing the return payload and does so enumeratively (title, USD price range, active-listing count, primary listing ID, condition, URL). Combined with coverage of auth, side-effect absence, and the three failure cases, nothing an agent needs to invoke this correctly is missing.

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% and the schema already defines slug as coming from a product URL or search result, so the baseline is 3. The description adds a small but real extension by admitting "product or listing slug" and by specifying that a missing slug yields a tool error, which sharpens what counts as valid input beyond the schema text.

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 ("Look up current public offer facts for a known product or listing slug") and immediately scopes it to the public-side data model, which distinguishes it from seller-side siblings like supercatch_get_listing and supercatch_get_store_inventory. An agent can tell this apart from the search_* tools without opening the 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 an explicit precondition ("Use when a product has already been identified") plus explicit exclusions ("Keyword discovery and seller-private inventory are outside this lookup"), which routes the agent to supercatch_search_listings / supercatch_search_marketplace for discovery. When-to-use and when-not-to-use are both present.

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