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

Annotations already cover read-only/idempotent/non-destructive, and the description adds genuinely new operational context: pagination, required scope billing:read, zero cost per read, and the need for the caller's own API key via Bearer auth. That is useful pre-call information an agent cannot get from the annotations.

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 operational facts are front-loaded (endpoint, purpose, scope, cost, auth), which is good. However the description is fully duplicated in French, roughly doubling length without adding information an agent needs, and the leading endpoint string largely restates the tool's own path.

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?

With no output schema and 5 optional parameters, the description should say more about what a 'line' actually contains and what happens with omitted from/to. 'One line per pull' is suggestive but leaves the return shape and defaults underspecified for a billing tool an agent must call correctly.

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 80%, so the schema already documents to/from/cursor/rf_account_id; the description adds nothing about any parameter. Notably 'limit' has no schema description and the description does not compensate, nor does it explain default date-range behavior when from/to are omitted (all params optional). Baseline 3 applies.

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 the endpoint (GET /v1/billing/usage) and describes the resource concretely: 'the documents behind GET /v1/billing, one line per pull, paginated.' This implicitly separates it from the sibling billing_get (summary) by framing this as the per-line breakdown. Not a crisp verb+resource phrasing, but an agent can tell the two billing tools apart.

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?

Usage is only implied: you call this to enumerate per-pull fee lines behind the billing summary. It never explicitly says 'use billing_get for totals, use billing_usage for line items' nor names any exclusion. The 'billing reads cost 0' note is a mild incentive to call it, but not real when-to-use guidance.

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