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

Annotations already declare readOnlyHint and closed-world, and the description adds substantive context on top: the merchant-key auth requirement with a specific error code, and the fact that revoked grants are excluded from results. It also explains the two grant modes and what each permits, which is behavioral information not present in annotations.

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?

All content earns its place, but it is delivered as one long sentence with a parenthetical nested inside another parenthetical (mode definitions inside the field list), which makes it harder to parse than necessary. Front-loading the resource identity is good; the structure could be broken into two or three sentences for readability.

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 inputs, an output schema present, and annotations covering the safety profile, the description supplies the remaining essentials: auth requirement, revoked-grant exclusion, and interpretation of the mode/scopes fields. Nothing critical to calling it correctly appears to be missing, though it says nothing about result volume or ordering.

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?

The tool takes zero parameters, so the schema imposes no semantic burden and the baseline is 4. The description correctly spends no space on nonexistent inputs.

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 names a specific resource (grants — partners allowed to act for your store) and enumerates the exact fields returned (grant_id, partner, mode, scopes, created_at, webhook endpoint ids). It is clearly distinguishable from mutation siblings like grant_revoke, though the verb is implied rather than stated and no sibling is named explicitly.

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 concrete usage prerequisite — merchant key only, and a grant key yields 403 grant_key_not_allowed — plus the scoping rule that revoked grants are not listed. It does not explicitly say when to prefer this over other listing tools, but the auth constraint functions as a clear call condition.

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