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

Annotations already establish the safe read-only profile, so the bar is lower, but the description adds a genuinely important behavioral fact: an empty result is a legitimate answer, not an error, because the product cannot be purchase-ordered until linked. That EMS relationship is not derivable from the annotations or schema. It does not cover result shape details such as cost fields beyond the passing 'at what cost'.

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-loaded with the directional framing, then the questions it answers, then the edge case. Three sentences, each carrying distinct information, with no padding.

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 only one parameter, the description does the needed work: it states what comes back (suppliers plus cost) and how to interpret an empty result. Only minor gaps remain, such as whether multiple supplier entries are grouped per item, which is not critical to invoking the tool.

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 single parameter carries its own description ('Product id from get_products'). The description restates that the id comes from get_products but adds no format or constraint detail beyond the schema, so the 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 (which suppliers carry a product's items) and adds the crucial scope marker 'the other direction', which distinguishes it from the sibling hub_get_supplier_items. An agent can tell the two apart without opening either 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?

Names concrete use cases ('who can I reorder this from', 'who is cheapest', 'am I buying this from more than one place') and points at get_products as the parameter source. It implies the alternative via 'the other direction' but never states an explicit when-not-to-use condition.

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