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

Beyond the readOnlyHint/openWorldHint annotations, the description discloses the match outcome taxonomy (exact/likely/ambiguous/none), what runner_up and rows contain, that misses are recorded as demand, that unavailable-price products are still returned under a readiness flag, and that buy_url responses carry a commission disclosure. That is substantive behavior an agent could not infer from structured fields.

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?

One dense but front-loaded paragraph that moves from inputs to match semantics to return contents to edge cases, with no filler sentences. It is on the long side, though every clause carries information the agent needs.

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 return-value burden and does so: it explains match values, products[0] contents, shelf_context, readiness, and the disclosure field. Nothing essential for correct invocation or interpretation appears 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 description coverage is 80%, so the schema already documents query, category, identifiers, and user_signature. The description adds marginal detail — that a barcode may be embedded in the name string and that brand+model resolves mpn/model_number — but says nothing about user_signature's quota/attribution role or category scoping beyond what the schema states. Baseline 3 fits.

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 one specific product') and enumerates the accepted identifier forms (name, ASIN, UPC/EAN/GTIN, brand+model), which makes the shape of the operation unambiguous. It does not explicitly contrast itself with search_products/get_products, so sibling differentiation is left to inference.

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 enumerations of acceptable inputs imply when this tool applies (you know the exact product or an identifier). But there is no stated 'use search_products instead when you only have a vague need' exclusion, and no mention of prerequisites such as needing at least one of query/brand/identifiers despite zero required parameters.

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