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

Annotations already declare destructiveHint=true, idempotentHint=false, and openWorldHint=false, so the safety profile is known. The description adds meaningful context beyond that: existing messages are untouched (clarifying the blast radius of the destructive action) and the tool remains available during offline or past-due states, which is non-obvious availability behavior.

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?

Four short sentences, each carrying distinct information, with the core action and effect front-loaded. Slightly sentence-fragmented, but no filler or repetition.

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 single-parameter delete tool with no output schema, the description covers effect, scope of impact, and availability under degraded account states, which is close to sufficient. It leaves out whether the deletion is reversible or how to recover a deleted rule, a minor gap given destructiveHint already signals irreversibility.

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 the single 'id' parameter is documented in the schema as 'Rule ID returned by list_mail_rules.' The description adds no parameter detail beyond that, 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 specific verb (delete) and a precisely scoped resource (SuperMailbox rule), and immediately clarifies the effect ('so it will no longer act on future incoming mail'). It also disambiguates from a similar-sounding category ('not provider-native filters'), so an agent can separate it from sibling rule tools like list_mail_rules and update_mail_rule.

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?

Gives useful context: it remains usable even when the mailbox is offline or billing is past due, and it explicitly scopes the operation to SuperMailbox rules rather than provider-native filters. It does not state a when-not case or name the alternative tool to use for editing a rule instead of deleting it, so it falls short of full routing guidance.

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