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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds no extra behavioral context beyond confirming a list operation, which aligns with the annotations but does not enrich them (e.g., no mention of pagination, ordering, or response format). This is adequate but not exceptional.

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?

The description is a single, concise sentence that efficiently states the function. It is front-loaded with the core purpose and contains no filler. However, it could arguably be slightly more detailed without losing conciseness, hence not a perfect 5.

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?

Given the simplicity of the tool (three optional filters, no output schema, read-only), the description is minimally sufficient. However, it lacks details about the return structure or any behavioral nuances, which might matter for an agent deciding how to process results. It is borderline adequate, so a 3 is fair.

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 100% and each parameter has a clear description in the schema. The description adds no additional meaning beyond what the schema already provides. Following the baseline for high coverage, a score of 3 is appropriate.

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 clearly states the action ('List') and the resource ('subscriptions (subscribers)'). It is unambiguous and uses a specific verb. It does not explicitly differentiate from sibling tools like getSubscriptionPlans, but there is no direct sibling for listing subscriptions, so the clarity is sufficient.

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 description provides no guidance on when to use this tool versus alternatives. It does not mention any prerequisites, limitations, or typical use cases. An agent would have to infer context from the tool name and parameters alone, which falls short of helpful usage guidance.

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