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

The annotations declare readOnlyHint=true, and the description aligns with that (list operation). The description adds behavioral details beyond annotations: cursor-based pagination, the response shape '{ onetimes }', and the API endpoint. No contradictions.

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 three sentences that front-load the core purpose, then pack in filters, response shape, and critical pagination rules. No redundant words; every sentence earns its place.

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 no output schema, the description mentions the response object '{ onetimes }'. It covers purpose, filters, pagination details, and the API endpoint. The only minor gap is not describing the structure of individual one-time items, but for a list tool this is acceptable.

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% with good descriptions for each parameter. The description adds some extra context about pagination cursor behavior and response format, but the schema already documents each parameter's purpose. The added value is moderate, 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 states the tool lists 'one-time (non-recurring) line items' with optional filters, which is a specific verb+resource. The sibling list tools (e.g., list_subscriptions, list_charges) are differentiated by resource name, so no ambiguity.

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 explains when to use filters, but more importantly, it gives explicit pagination instructions: 'when paging with cursor, omit every other filter'. This is valuable guidance. However, it doesn't explicitly state when NOT to use this tool versus other list tools, though context makes it clear.

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