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

Annotations already declare readOnly/destructive=false and openWorldHint=false, so the safety profile is covered. The description adds behavioral context beyond that: results are limited to the exact item match and 'similar listings kept apart,' telling the agent what is intentionally filtered out of the response. It does not discuss rate limits or freshness, but with annotations and an output schema present the bar is lower.

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?

Three tightly packed sentences: scope first, then parameter guidance, then an example. Every element is used and front-loaded, though the opening fragment is dense and slightly telegraphic compared to plain prose.

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 only two parameters, full schema coverage, annotations, and an output schema, the description covers what is needed to call it correctly and what the results represent. Minor omissions (freshness or latency of seller data) are not essential for invocation.

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 baseline is 3, but the description goes further by explaining the alternative ?variant= URL form for multi-option products and pairing it with a worked example, which clarifies when variant_id matters. That is genuine added meaning over the schema's terse 'Option to price' field.

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?

The description states a specific operation and scope: it returns other sellers of the exact same item (matched by catalog ID or barcode), scoped to one variant, with similar-but-unrelated listings deliberately excluded. That is precise enough to separate it from search_products or get_product, though it never explicitly contrasts itself with those siblings by name beyond citing get_product as a variant_id source.

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?

It gives a clear condition for the optional parameter ('Pass variant_id ... or a ?variant= URL for multi-option products') and shows a concrete call example, which tells the agent when variant_id is needed. It stops short of stating when not to use this tool versus search_products, so it is clear context without explicit exclusions.

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