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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds real behavioral value beyond that: a result cap (default 50, max 200) and deterministic ordering (newest first). It does not describe pagination or the returned PO shape, but the core behavioral traits are disclosed.

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 dense sentences with zero filler, front-loading the resource and scope before the filters and the invoice-line use case. Every clause conveys information the agent needs.

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 needn't detail return fields, and it adequately covers filtering, ordering, and result limits. Minor gaps are the unpaginated cap behavior and the lack of explicit routing to sibling retrieval tools.

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?

With 0% schema description coverage, the description carries the full burden and largely meets it: it defines the status enum (open|closed), explains sku as "a SKU that appears on the PO lines," and gives limit's default and maximum. vendor_id is only implied by "for a vendor," so one parameter remains slightly under-specified.

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 resource and scope ("Purchase orders for a vendor") plus the two optional filters, so the agent immediately knows this returns a filtered set rather than a single PO. The vendor-scoped, multi-result framing implicitly separates it from the sibling get_po which fetches one PO.

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?

Provides a concrete when-to-use scenario ("filter by sku to find the PO for an invoice line"), which is genuinely helpful context. It stops short of naming alternative siblings (get_po, search_invoices) or stating when-not to use this tool, so it is clear context without explicit exclusions.

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