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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower. The description adds genuine context beyond them: it discloses the required auth scope ('Needs read') and that the tool self-reports incomplete coverage ('reports what it could not cover'), which is unusual and useful.

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 compact clauses with the resource and scope front-loaded and no filler. 'Needs read; every plan' is terse to the point of being slightly cryptic, but it still earns its place as a permission note.

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 should carry more of the return-shape burden. It hints at partial results ('reports what it could not cover') but never explains the continue/pagination flow, which is material for a tool with a 4096-char cursor parameter.

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 80% and the schema already documents each parameter, but the description adds behavioral meaning: 'optionally later ones' ties include_later to intent, and 'across one or all mailboxes' clarifies the account parameter's scope. It doesn't cover the continue token, which is the one real gap.

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+resource (lists follow-ups and snoozed messages) and scopes it to one or all mailboxes. It clearly differs from write-side siblings like set_followup and wake_snoozed, though it never names those alternatives 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?

The description implies when the tool applies ('due follow-ups', 'optionally later ones', 'snoozed messages'), but gives no explicit when-to-use vs. when-not guidance relative to siblings such as wake_snoozed or set_followup. Usage must be inferred from the scope clause.

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