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

The annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is well covered. The description adds the useful 'active billing context' scoping detail, but does not mention return format, ordering, pagination, or other behavioral nuances. With annotations carrying the safety burden, this is adequate but not rich.

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 sentence with no filler. It front-loads the action, resource, and scope, making it easy for an agent to parse and act on quickly.

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 simple, read-only list tool with one optional parameter and robust annotations, the description is largely complete. It could mention what fields are returned or clarify how the active billing context is determined, but an agent can likely invoke this tool correctly based on the name, scope, schema, and annotations.

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?

The input schema fully documents the only parameter, limit, including default, minimum, and maximum. The description adds no parameter-level meaning, but since schema coverage is 100%, the baseline 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 states a clear verb ('List'), a specific resource ('invoices'), and a scope ('active billing context'), which is enough to distinguish it from the many sibling list tools like account_list, connector_list, or file_list. It is not a tautology and immediately tells an agent what the tool does.

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 'for the active billing context' gives a clear context for when the tool applies. However, it does not explicitly discuss when not to use it or name alternatives for other billing-related operations such as credits_usage or subscription_manage, so it falls slightly short of fully explicit usage guidance.

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