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

Annotations already declare readOnly/non-destructive, but the description adds the crucial behavioral fact that no structured commercial-terms data is returned at all—only an explanation of the API limitation. That is exactly the kind of disclosure an agent needs and cannot get from the annotations. It does not mention auth or rate-limit behavior, keeping it at a 4.

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?

Two dense sentences that front-load the key point (SP-API does not expose commercial terms) before the redirect targets. No filler, though the phrasing is slightly terse and could be one clause clearer.

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 optional parameter, the description carries the return-value burden and does so by explaining that the response is a limitation notice plus redirect. Combined with the fully documented schema, an agent has everything needed to call and interpret it; only format specifics of the explanatory payload are omitted.

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% and there is a single optional account_id whose meaning (outpost/seller + marketplace, see list_clients) is already fully documented in the schema. The description adds no parameter-level detail, 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?

The description states a specific and unusual purpose: the tool does not return trading terms, it returns an explanation that SP-API does not expose commercial terms in read mode, and it redirects to Vendor Central. It names the sibling get_vendor_remittances as the path for netCost per PO, so an agent can distinguish it from the other vendor tools without opening a 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?

It effectively tells the agent when this tool applies (looking for payment terms/discounts/agreements) and routes to the right alternative for netCost (get_vendor_remittances) plus Vendor Central. There is no explicit 'do not use for X' exclusion, so it stops just short of a full when/when-not statement.

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