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

Annotations already declare a safe, read-only, closed-world read. The description adds real behavioural content beyond them: the aggregation collapses multiple sender addresses into one row and includes a computed count of how many senders can be unsubscribed without a human opening a page. It does not cover pagination or the full returned row shape.

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?

Two sentences, no filler, and the grouping concept is front-loaded. The clause about unsubscribable senders is slightly convoluted and the deferral to listSubscriptions would be better placed last.

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 list tool with no output schema and seven undocumented optional filters, the description leaves significant gaps: it does not explain the filter semantics, sorting behaviour, or the full row contents. It is adequate for understanding intent but not for calling it correctly with non-default parameters.

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 0% across seven parameters, so the description must compensate and does not. 'Takes the same filters as listSubscriptions' only points at a sibling and explains nothing about sort, query, status, address, or suggested.

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?

It states a specific resource — subscriptions grouped by sender domain — and explains the aggregation semantics (one row per company even with multiple sending addresses). It implicitly separates itself from listSubscriptions ('the same subscriptions') but does not use a clear verb or name the sibling 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 phrase 'the same subscriptions grouped by sender domain' implies you use this instead of listSubscriptions when you want a per-domain view. However, there is no explicit when-to-use/when-not-to-use guidance, and neighbouring tools like unsubscribeSubscriptionDomain or moveSubscriptions are not referenced.

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