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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description still adds value by scoping the lookup to 'the connected owner's' subscription and explicitly denying any charge or billing modification, which are behavioral facts not encoded in the annotations.

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 short sentences, zero filler. The core purpose is front-loaded and the caveat about not touching billing follows immediately after.

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?

With an output schema, a zero-parameter input, and full annotation coverage, the description needs only to state what is checked and that it is side-effect free. It does both, so an agent has everything required to call it correctly.

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?

The tool takes no parameters, so there is nothing for the description to disambiguate. Baseline of 4 applies; the description correctly implies the owner is derived from connection context rather than supplied as an argument.

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 ('Check') and a specific resource ('the connected owner's alerts subscription is active'), plus the states covered (pre-payment, post-expiry). An agent can distinguish it from start_subscription or get_plan by the 'status check' framing, though no sibling is named 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?

Gives clear usage context — check before payment or after expiry — which tells the agent when this is the right call. It also implicitly excludes billing-mutation tools via 'does not charge or modify billing', but it never names an alternative such as get_plan or start_subscription.

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