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

readOnlyHint=true already tells the agent this is a safe read. The description adds useful context that the response includes lines, supplier and totals, but says nothing about auth, errors, or behavior for a non-existent Guid. With annotations covering the safety profile, a 3 fits.

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 compact sentences with the core purpose front-loaded and no filler; the trailing API endpoint reference is mildly redundant but harmless for an agent familiar with the Unleashed API.

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-resource read with a fully documented 1-parameter schema and read-only annotation, the description covers what is needed and even sketches the return payload since no output schema exists. Minor gaps (error/not-found behavior) remain.

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% and the single orderGuid parameter is fully documented in the schema. The description only restates 'by Guid' and adds no format or semantic detail beyond the schema's pattern and description, 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?

States a specific verb ('Fetch') and resource ('purchase order') and adds scope details (by Guid, with lines, supplier and totals). 'Single' implicitly differentiates it from the list_purchase_orders sibling, though the sibling is never named explicitly.

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?

The phrase 'by Guid' implies it should be used when a specific order identifier is known, but there is no explicit when-to-use guidance or routing against list_purchase_orders / unleashed_get_sales_order. Usage must be inferred.

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