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

Annotations only declare the safe-read profile; the description goes well beyond by disclosing that due-date rates may be unavailable, that undated invoices are excluded from driver rows and surfaced separately via undated_invoice_count / undated_base_amount / undated_by_currency, and how P&L is split. These are non-obvious behavioral traits an agent cannot get from structured fields.

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?

Four sentences, all carrying distinct information (scope, ordering, P&L split, undated handling, use cases), with the primary purpose front-loaded. The undated-invoice sentence is dense but earns its place by preventing a common misinterpretation.

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 an output schema present, the description need not explain return values, and it still covers scope defaults, edge cases, and intended use cases. Nothing an agent needs to invoke or interpret this read-only report 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 description coverage is 100% and both optional parameters are already fully documented (currency ISO pattern, entity_id from list_entities, omit-for-workspace semantics). The description adds the 'by currency' framing but no additional parameter syntax or defaulting nuance, so the 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?

The description names a specific verb and resource ('Returns overdue invoice drivers by currency and top contact'), states the ordering logic ('prioritised by largest exposure per currency'), and describes the exact output decomposition (unrealised FX P&L vs since-due P&L). An agent can distinguish this from the many other cashflow/exposure siblings without opening a schema.

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?

It gives concrete triggering questions: 'what is driving overdue invoices?' and 'what did overdue invoices cost us?', which clearly frames the intended use. There are no explicit exclusions or named alternative tools, so it falls short of a 5.

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