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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds useful domain context about delivery stopping after cancellation, which helps the agent interpret the status meaning, but it does not disclose return format or error behavior.

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 two concise sentences with no filler. The first sentence front-loads the returned fields and the second provides a practical warning, though the first sentence is a noun phrase rather than a clear verb-led statement.

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 low-complexity tool with one documented parameter, no output schema, and safety annotations, the description adequately covers what data is returned and when to use it. It does not mention error cases or status value meanings, but these are not essential for basic invocation.

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 only parameter, 'brand', is already described as a 'Brand slug.' The description's phrase 'for a brand' adds no new semantic detail beyond what the schema provides, so baseline 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 identifies the resource (brand subscription) and the data returned (plan, status, renewal date, add-ons), though it lacks an explicit verb like 'retrieves' or 'gets.' It is distinct from sibling tools like brand_get or plan_list because it focuses on subscription-specific fields.

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?

It gives a concrete use case: check this before assuming packages will keep arriving, since delivery stops when a subscription is cancelled. It does not name alternatives or explicit when-not-to-use conditions, but the guidance is actionable and clear.

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