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

Annotations cover the safe, idempotent, non-destructive mutation profile, so the bar is lower. The description genuinely adds behavior beyond them: following triggers an email when the idea ships, delivered under the 'Product news' topic, and the recipient can unsubscribe in-app. It does not say what happens when the person is already following, but the added context is substantive.

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?

It is short, but the single sentence is malformed — a run-on with a missing separator and the notification condition front-loaded instead of the action. Word count is appropriate; clarity and front-loading are not.

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 simple one-parameter tool with no output schema and informative annotations, the description is roughly adequate. It omits the repeat-call behavior (though idempotentHint=true covers it) and any pointer to unfollow_idea, so an agent still has to infer the action's meaning from the tool name.

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?

There is a single parameter with 100% schema description coverage and a documented pattern, so the schema already carries the semantics. The description adds nothing about idea_id or how to obtain one, which matches the baseline 3 when schema coverage is high.

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 explains the consequence of following (email notification when the idea ships) but never states the action itself in verb+resource form, and its wording is garbled ('The person hears by email when it ships Sent under the Product news email topic'). An agent can infer it registers a follow/subscription, but the purpose is only implied rather than stated.

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?

There is no when-to-use guidance, no prerequisites, and no mention of alternatives such as unfollow_idea (the inverse) or vote_for_idea (a different form of engagement) among the many siblings. The opt-out clause describes a setting in the app, not how or when to invoke this tool.

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