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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds only the scope of retrieval (single record by Id) and a deduplication hint; it says nothing about what is returned, not-found behavior, or pagination, which is a modest but not severe gap for a read tool.

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 front-loaded sentence with the verb, resource, and key stated first; the trailing conditional is slightly cryptic but short. No padding.

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 single-record read with annotations covering safety and no output schema to explain, the description is nearly sufficient; only not-found/error behavior is unaddressed, which is a minor omission.

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 both 'id' and 'company' are already documented in the schema, and the description adds no format, realm-id, or multi-company detail beyond it. Baseline 3 is appropriate when the schema carries the full parameter burden.

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 ('Get a single purchase order') with the identifying key ('by Id') and the source system (QuickBooks Online). It is distinguishable from search_purchase_orders, though it names no sibling explicitly and its trailing clause mixes usage guidance into the purpose statement.

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?

'when no search or write answer already holds it' gives a genuine usage condition (avoid a redundant fetch when a list/search or create response already returned the record), but it never names the obvious alternative (search_purchase_orders) or states when this tool is required.

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