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

Annotations already declare readOnly, idempotent, non-destructive safety, so the bar is lower. The description adds real behavioral value beyond them: amounts are bare numbers and currency requires a separate call, which prevents an agent from mis-stating monetary values.

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 tightly scoped sentences, front-loaded with what the tool returns and followed by the one non-obvious data caveat. Nothing is redundant.

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 read-only single-record tool with annotations covering safety and no output schema, the description lists the salient return fields and the currency caveat, which is enough to use it correctly. It stops short of describing pagination or nested structures, but none appear relevant 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?

The single `id` parameter is fully documented in the schema (100% coverage), so the baseline is 3. The description adds no syntax or format detail about the id beyond what the schema already provides.

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 (Get) and resource (purchase order) and enumerates the returned fields (amount, status, vendor, linked project). It clearly reads as the single-record counterpart to list_purchase_orders, though it never names that sibling to make the distinction explicit.

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?

No explicit when-to-use versus list_purchase_orders or get_purchase_order_line. The currency note does give a useful follow-up workflow step (call get_organization_settings), which is implied usage guidance rather than a selection rule.

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