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

readOnlyHint=true already tells the agent this is a safe read. The description adds value by disclosing the returned metric categories and the derived 'when sessions run out' figure, which annotations cannot convey. It does not say whether multiple subscriptions are returned, how pauses are treated numerically, or the shape of the response.

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 filler; every listed metric maps to something an agent would look for. It is a noun phrase rather than a full clause, 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?

With no output schema, the burden of describing what comes back is on the description, and it does enumerate the key fields. Missing are whether results are grouped per subscription, whether historical packs are included, and any date/period scoping — details an agent may need before trusting the numbers.

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?

Only one parameter and schema coverage is 100%; the schema already documents clientId as the client's User _id sourced from list_clients. The description adds no additional constraint or format detail, so the 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?

Names a specific resource (per-subscription session pack usage for one client) and enumerates exactly what the agent will learn: allowance, used, left, upcoming, no-shows, pauses, and exhaustion timing. It is clearly a read/report tool and distinct from siblings like list_sessions or get_client_progress, though it never states a verb 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?

No when-to-use guidance, no alternatives named, and no prerequisites. The agent must infer from the name that this is the right call for 'how many sessions does this client have left' versus list_sessions or list_subscriptions.

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