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

Annotations already mark this as non-read-only and non-idempotent, so the description only needs to add context, and it does: it returns PO number and totals, inherits currency/VAT/buyer block from the shared profile, and states the 5-document monthly free quota. These details do not contradict the annotations and are genuinely useful.

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?

Three sentences, front-loaded with the main purpose, then key defaults and the quota. There is no filler. It loses one point because the second sentence uses 'unit_price' instead of the schema's unit_price_minor, creating an avoidable ambiguity in an otherwise compact structure.

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?

There is no output schema, so the description's mention of PO number and totals is valuable, and the quota note is useful. However, the central monetary parameter is described incorrectly, which is a critical completeness failure for a PO creation tool; an agent cannot safely call it correctly without spotting and resolving the contradiction with the schema. It also does not state that repeated calls will create new documents, though the annotation covers that.

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 schema documents all 11 parameters, so the baseline is 3, but the description actively contradicts the schema: it says 'unit_price is in MAJOR units' while the actual parameter unit_price_minor is documented as MINOR units with examples (9000 = 90.00 EUR, 90 = JPY 90). An agent following the description would format amounts incorrectly by a factor of ~100, and it also references a parameter name that does not exist.

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 uses a specific verb ('raise') and resource ('purchase order to a supplier from items'), and states the concrete outcome: return its PO number and totals. This clearly distinguishes purchase_order_create from siblings like credit_note_create, purchase_order_get, and purchase_order_delete.

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 description's context is clear: use this when raising a PO from items. It does not, however, name alternatives or exclusion conditions (e.g., use purchase_order_get to retrieve a created PO, or credit_note_create for supplier credits), so the guidance is implied rather than explicit.

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