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

Annotations already declare this is not read-only, is idempotent, and not destructive, so the safety profile is covered structurally. The description adds only that notices stop and where the credentials come from; it does not say whether unsubscribing is permanent, what happens on an invalid or expired signature, or whether confirmation is required.

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?

A single front-loaded sentence with no redundancy; the essential action is stated first and the parameter hint follows. It is slightly cryptic in the parenthetical, but nothing is wasted.

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 two-parameter mutation tool with no output schema, the description covers the action and the origin of the credentials but omits failure modes, reversibility, and confirmation behavior. Annotations carry idempotency and safety, leaving the description adequate but incomplete.

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 the baseline is 3, and the description adds provenance the schema lacks: both id and sig originate from the user's unsubscribe_url rather than being arbitrary values. It stops short of describing signature validation or the 'sub_...' id format already implied by the schema.

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 verb and resource ('Stop update notices'), which clearly distinguishes it from the sibling subscribe_updates and get_updates. It falls short of a 5 only because it does not explicitly name those siblings as counterparts.

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 parenthetical '(id + sig from your unsubscribe_url)' implies this is used with a link the agent already received, giving some usage context. However, there is no explicit when-to-use statement, no mention of the subscribe_updates alternative, and no note about prerequisites such as possessing a valid signed link.

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