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

Annotations only cover the read-only/open-world safety profile; the description goes well beyond that by decoding the `orderable` flag, warning that a listing is catalogue identity rather than availability, and forbidding presenting an `orderable: false` chain as purchasable. Since no output schema exists, this is the only place that semantics is disclosed.

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?

Front-loads purpose and the routing rule before the longer `orderable` explanation, and every sentence carries real meaning. Slightly long, and the final aggregate sentence partially overlaps the earlier warning, but nothing is filler.

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 and zero required parameters, the description supplies exactly what is missing: the shape of the response (per-chain listings with item code, name, package size) and the interpretation of the `orderable` flag. An agent can call and correctly use the result without further context.

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 documents the UUID format and the precedence rule ('used only if product_id is omitted'). The description restates the same keys and formats without adding new syntax or constraints, 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?

Names a specific verb and resource ('Fetch full detail for one canonical product') and identifies both lookup keys (product_id UUID or GTIN barcode). It also lists the returned content (per-chain listing with item code, display name, package size), which separates it cleanly from search_products.

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 states when to call it: 'after search_products to confirm identity, or directly when the GTIN is already known.' The sibling tool search_products is named and the condition selecting this tool over it is spelled out.

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