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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds two things beyond that: an authentication requirement (sign-in) and an ownership restriction (only lists the shopper owns are visible), which materially affect whether a call succeeds. It does not say what happens for a list_id the shopper does not own, but the added context is real.

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 sentences, zero filler, with the scope and the shape of the answer front-loaded before the prerequisite. The field enumeration earns its space because no output schema exists.

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, the description correctly fills the gap by listing what the result contains, and it flags the sign-in prerequisite. Minor gaps remain: ordering or pagination of invitations and the behavior for an unowned or invalid list_id are unstated.

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 list_id and market are already documented in the schema. The description adds no syntax, default, or meaning for either parameter beyond restating the ownership condition, 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 gives a specific verb ('Returns'), a precise resource (the people a list is shared with), and a scope constraint (a list the signed-in shopper owns). It also enumerates the returned fields (share_id, email, role, accepted), which separates it cleanly from the sibling write tools share_wishlist and revoke_share.

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?

Usage is only implied: the read-only listing of existing shares makes sense before share_wishlist or revoke_share, but neither sibling is named and no exclusion is stated. The one explicit prerequisite, 'Requires sign-in,' is useful but is not a when-to-use rule.

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