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

With no annotations provided, the description must carry the behavioral disclosure burden. It does disclose meaningful behavior: results are ordered newest first, scoped to the account, and contain statement keys for use with get_statement. However, it does not explicitly state that this is a read-only operation or describe any response shape or edge cases, leaving some behavior implicit.

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 clause that packs in the key facts: scope, ordering, returned content, and the downstream relationship to get_statement. Every word earns its place, with no repetition of the tool name or schema details.

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 optional-parameter list tool with no output schema and no nested objects, the description covers the essential context: what is returned, in what order, and why it matters. It could explicitly say 'use the returned key as the statement identifier argument to get_statement', but the current phrasing is sufficient for a low-complexity tool.

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 already documents the lone parameter 'limit' with a description and default of 12, so schema coverage is 100%. The tool description adds no additional parameter meaning beyond that, which matches the baseline of 3.

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 defines the resource as the account's billing periods with their statement keys and notes the newest-first ordering. It also references get_statement, distinguishing this listing operation from that retrieval sibling. The main verb is only implied by the tool name rather than stated explicitly, so it stops just short of a 5.

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 get_statement' indicates that this tool is used to obtain statement keys that are then passed to get_statement, giving clear context for when to use it. It does not explicitly state alternatives or when not to use it, but the intended workflow is reasonably clear.

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