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

Annotations already establish read-only, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds the return shape (lines with qty_received/qty_invoiced plus linked invoice ids), which is useful given there is no output schema, but it says nothing about failure behavior when the PO doesn't exist.

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 most important content (what the PO object contains). It wastes no words, though the fragmentary phrasing means little is actually conveyed.

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 simple one-parameter read whose annotations cover the safety profile, the description partially compensates for the absent output schema by outlining the returned PO structure. However, it omits the parameter's meaning and any failure/not-found behavior, leaving meaningful gaps.

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 0% for the single parameter, po_number, and the description never mentions it or clarifies its format or source. The parameter is self-evidently named, which limits the damage, but the description fails to compensate for the documentation gap as required at this coverage level.

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 is a noun-phrase fragment ('A purchase order with lines...') that describes the resource's contents rather than stating a verb like 'retrieves a single purchase order by number.' The title supplies the verb, but the description itself doesn't clearly distinguish this single-PO fetch from siblings such as search_pos or link_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?

There is no when-to-use guidance, no mention of alternatives like search_pos, and no note about prerequisites such as needing a valid po_number. The agent is left to infer the tool's role from the name alone.

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