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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed world), so the description's job is to add substance — which it does by describing the returned structure (lines, receipts, bills, match verdict) in the absence of an output schema. It stops short of noting behavior for a missing or unknown PO id.

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?

A single compact sentence that front-loads the scope ('One order') before enumerating contents; every clause carries information. The grammar is slightly elliptical ('each line with what was ordered'), but nothing is wasted.

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 one-parameter read tool with no output schema, the description gives a usable picture of the response shape and match semantics. Only edge-case behavior (unknown po_id, what an unmatched bill looks like) is unaddressed, which is minor here.

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?

Only one parameter (po_id) and schema description coverage is 100%, with the schema itself giving the 'PO-0001' format example. The description adds no parameter-level detail, 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 states a specific resource ('One order') and enumerates exactly what the caller gets back: line-level ordered/received/billed quantities, receipts, bills, and bill-match status. 'One order' implicitly contrasts with the plural p2p_pos, but no sibling is named explicitly, so sibling differentiation is left to inference.

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?

Usage is only implied — the agent can infer this is the drill-down for a single PO after seeing it in p2p_pos, but the description never says when to use this versus p2p_bill_match, p2p_unbilled_receipts, or p2p_pos, and offers no exclusions.

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