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

Annotations already declare write semantics (readOnlyHint=false, destructiveHint=true, idempotentHint=false, openWorldHint=true), so the safety profile is covered. The description's main added value is the word 'draft', implying the order is created in an unsent/unapproved state, but it says nothing about retry behavior, whether the total is computed server-side, or what is returned for follow-up.

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 no filler. It is efficient, though the brevity leaves room that could have been spent on the when-to-use signal without bloating.

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 6-parameter mutation with no output schema and strong annotations, the description covers the core shape but omits what happens on success (created PO id/status), the 50-item cap, and the draft-to-send lifecycle. Adequate but with clear gaps an agent would hit on the first call.

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 coverage is 67% and the schema itself documents every parameter well, including the vendor_id→contact_id relationship and line-item semantics. The description restates the items/supplier/project shape but adds no formatting or validation insight beyond the schema, so 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 and resource ('creates a draft purchase order') plus key scope details (supplier, line items, optional project). It is immediately clear what the tool produces. It doesn't differentiate itself from adjacent crates like create_bill or create_estimate, which is the only thing keeping it from a 5.

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 guidance on when to use this versus create_bill, create_estimate, or create_sub_contract, and no stated prerequisites (e.g. that vendor_id must come from list_contacts). The word 'draft' implies the order isn't sent, but the agent must infer that and infer what the next step would be.

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