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

The annotations already declare readOnlyHint, idempotentHint, and destructiveHint. The description adds behavioral facts that are not in the annotations and cannot be inferred cheaply: results are ordered 'newest first', and 'amounts are in major currency units' prevents the caller from interpreting amounts as cents. It does not say what happens when the limit is reached or whether there is more data beyond the returned page.

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 with no padding. The scoping and ordering information is front-loaded, and the currency-unit caveat follows immediately where it is needed.

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?

The output schema is present, so the return shape needs no explanation in the description, and the ordering and unit conventions are covered. For a one-parameter list tool whose read-only safety profile is already covered by annotations, the only real gap is pagination or truncation behavior.

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 schema has 100% description coverage: the single 'limit' parameter is fully documented with its default and its max of 50. The description adds nothing about that parameter, so the baseline score is 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 uses a specific verb and resource ('List the authenticated user's invoices'), and it scopes the results to one user. That scope alone distinguishes it from the other account_* siblings, but it never names account_invoices_get, the tool for retrieving a single invoice, so the caller must infer from the description that 'get' returns one invoice while this tool returns a list.

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?

Only implied usage: listing invoices for the authenticated user. There is no statement of when to prefer this over account_invoices_get, no note that pagination or a limit is the way to get more results, and no exclusion conditions. The name largely carries the routing decision.

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