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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, non-destructive), so credit goes to what the description adds: a non-obvious data-representation caveat that amounts are bare numbers with no currency, plus the required companion call to get_organization_settings. That is genuine behavioral context beyond the annotations, though return shapes and search behavior remain unstated.

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?

Three tight sentences with the core purpose front-loaded and no filler. The currency sentence, while slightly tangential to listing, is high-value and well-placed at the end rather than buried.

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, the description carries the return-value burden, and it usefully discloses that amounts are uncurried bare numbers requiring a currency lookup. It stops short of describing the list item shape or pagination default, but the currency caveat covers the highest-risk ambiguity.

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%, so the schema already documents status, vendor_id, project_id, page, per_page, and search. The description re-states the status enum values and the vendor/project filters that are already in the schema, adding no new parameter syntax or format detail; the baseline 3 applies when the schema does the work.

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 purchase orders") and enumerates the filter dimensions, which is clear enough to distinguish it from create/update/delete purchase order tools. However it does not differentiate itself from close siblings like list_purchase_order_lines, list_purchase_order_links, or get_purchase_order, leaving the agent to infer scope from the name alone.

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 implicitly signals usage by listing status/vendor/project filter dimensions, and gives one concrete workflow instruction (call get_organization_settings for currency_code). But it never states when to prefer this over a sibling list or get tool, nor any exclusion criteria, so guidance is only implied.

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