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

The annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered without the description. The description's real contribution is disclosing the returned fields and the derived 'balance still due after any credit note', but it says nothing about result ordering, result caps, or pagination for what could be a large collection.

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 sentences, front-loaded with purpose followed by filtering capability; the field enumeration is dense but earns its place because no output schema exists. Slightly list-heavy, but nothing is redundant.

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 no output schema, enumerating the returned fields and the credit-note-adjusted balance is exactly the missing context an agent needs. The remaining gap is pagination/ordering behavior on a potentially unbounded collection, which is not addressed.

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 50%: 'from' and 'to' are documented as YYYY-MM-DD inclusive, while 'client' and 'status' have no schema descriptions. The description recovers the three filter dimensions (status, client, date range), which is modest compensation, but it adds no format or matching semantics for 'client' (exact id, name, or partial match) beyond what the schema already shows.

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 opens with a specific verb and resource ('List invoices') and immediately enumerates the fields each record carries, which separates it from invoice_get and overdue_report at a glance. The odd phrasing 'by number' would be better as 'with' given the fields listed are not numbers, but the intent is still unambiguous.

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?

'Filter by status, client and date range' implies how to narrow results, but there is no explicit when-to-use guidance, no statement of what an unfiltered call returns, and no reference to sibling tools such as invoice_get for a single record or overdue_report for outstanding balances.

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