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

Annotations only declare readOnlyHint=true, so the description's disclosure of the return shape ('array of { created, email }') is genuinely additive given no output schema exists. It does not discuss pagination behavior or rate limits, but it goes beyond the structured fields already provided.

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 short clauses: purpose, return shape, upstream endpoint. Nothing is padded and the core purpose is front-loaded in the first phrase.

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?

For a read-only, zero-required-parameter list tool, the description covers what the tool returns and which system it maps to, while annotations carry the safety profile and the schema carries pagination/time-range filtering. Nothing essential to correct invocation is missing.

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 limit, offset, start_time and end_time are already documented as integer fields with their meanings. The description adds no parameter syntax or format guidance beyond what the schema states, so the baseline of 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?

States a precise verb and resource – 'List globally-unsubscribed email addresses (the global suppression list)' – with the parenthetical disambiguating it from other suppression-type siblings such as sendgrid_list_bounces. It even pins the upstream endpoint, so an agent can identify exactly what set of records this returns.

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 implied by the resource name – an agent reading 'global suppression list' can infer it is for auditing addresses that have opted out globally – but there is no explicit when-to-use, when-not-to-use, or pointer to sendgrid_list_bounces as the alternative for a narrower suppression class. Adequate, not instructive.

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