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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed world), so the bar is lower. The description adds real value by disclosing what the response contains — derived status, next expected charge, per-currency monthly equivalent — which is important given there is no output schema. It does not mention ordering, volume, or behavior when no subscriptions exist.

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?

One dense sentence with no filler, front-loading the resource scope before the returned fields. It is efficient, though it reads as a noun phrase rather than a complete statement of what the tool does.

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 one optional parameter and no output schema, the description usefully enumerates the return fields. However it omits ordering, volume, and how as_of shifts the derived status, and it never routes the agent away from purch_get_subscription, leaving meaningful gaps for the agent to resolve.

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 coverage is 100% and the single optional parameter as_of is fully documented in the schema. The description does not mention as_of or explain how the evaluation date affects derived status and 'periods matched or missed', so it adds nothing beyond the schema. Baseline 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?

The description names the resource ('Every declared subscription') and enumerates the returned content: periods matched/missed, derived status, next expected charge, and monthly equivalent per currency. The scope word 'every' implicitly distinguishes it from the single-record sibling purch_get_subscription, though that sibling is never named.

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 mention of the alternative purch_get_subscription or purch_upcoming, and no stated prerequisites. The only hint is 'every', which implies a full listing but requires the agent to infer it.

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