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

readOnlyHint=true already tells the agent this is a safe read. The description adds the HTTP route (GET /usage) and paging-continuation behaviour, which is modest extra context, but says nothing about return shape, limits, or auth; the offset paging guidance largely duplicates the schema.

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?

Three short sentences, front-loaded with purpose then filters then paging, with the endpoint last. No filler or repetition.

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 read-only list tool with fully documented params and no output schema, the definition covers purpose, filterable fields, and paging. Minor gaps remain around return fields and any tenant/permission scoping, but nothing needed to call it correctly is missing.

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%, so the baseline is 3, but the description is the authoritative source for valid filter fields (line_item_id, external_key, from, to) — the schema itself defers to the description, so these names add real semantic value for the filters parameter.

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+resource+scope: listing 'usage (metered billing) data points recorded against subscription line items'. This differentiates it cleanly from sibling list tools such as chargeover_list_subscriptions and chargeover_list_invoices, so an agent knows exactly what entity is returned.

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?

Gives implied usage context via the filterable fields and paging hints, but never states when to choose this tool over siblings or what prerequisite conditions exist (e.g. a subscription line item must already exist). Adequate but inferential.

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