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

With no annotations provided, the description carries the full behavioral burden and largely fails to: it says paid + open invoices are returned but never addresses result size, pagination, ordering, or whether month can be used without year. The status inclusion is a useful trait, but the rest of the mutation-free read behavior is unstated.

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, front-loaded sentences with no filler; the resource is named first and the scoping note second. Nothing could be removed without losing information.

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?

There is no output schema and no annotations, so the description is the only source of behavioral context for a 2-parameter tool, and it is too thin. It says nothing about return shape, result size, or defaults when year/month are omitted, leaving an agent under-informed before calling.

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 0% and both parameters are undocumented in the schema, so the description does the compensating work by tying both to an optional year/month scope. It still omits format details (e.g., four-digit year) and the interaction between year and month, so the compensation is only partial.

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 (list) and resource (Stripe invoices) plus the included statuses (paid + open), which is more informative than a bare 'get invoices'. It does not explicitly contrast itself with billing siblings such as get_balance, get_subscription, or get_credit_transactions, so sibling differentiation is only implied.

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 phrase 'Optional year/month scope' hints that filtering is possible, but there is no explicit when-to-use guidance, no statement of when not to use it, and no pointer to an alternative tool for billing data. An agent must infer the use case on its own.

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