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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so "Read-only." adds no new information. The one piece of genuine added context is that results are scoped to the caller's own account, with no id argument to widen it. Return shape and default ordering are not described.

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?

Two short sentences, front-loaded with the resource and scope. The leading verb and scope come first, which is the right order. The trailing "Read-only." is redundant against the annotations and does not earn 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?

For a two-optional-parameter read-only list tool with full schema coverage and rich annotations, the description covers what an agent needs to call it correctly. With no output schema, it could have said what an invoice record contains, but the tool is simple enough that this is a minor gap.

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 description coverage is 100% – limit (max 100, default 20) and offset (default 0) are fully documented in the schema. The description adds nothing beyond that, so the baseline 3 applies; no meaning is missing, but none is contributed either.

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 and resource ("List ... billing invoices") with a clear scope qualifier: the merchant's own, tied to plan purchases. That distinguishes it well from payment-oriented siblings. It stops short of naming list_payments or get_payment as the contrasting option, so the boundary is implied rather than drawn.

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?

There is no explicit statement of when to use this versus list_payments or get_payment, both of which a naive agent might pick instead. The parenthetical "their plan purchases" hints at the domain, but no exclusion or trigger condition is given.

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