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

Annotations already declare destructiveHint=true, idempotentHint=true, and openWorldHint=false, so the risk profile is largely covered. The description does add the required 'purchase_orders:write' scope, which is genuinely useful authorization context. It does not explain whether updates are partial merges, which fields trigger destructive effects, or what happens to omitted fields.

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 short sentences, front-loaded with the core action and followed by the permission requirement. Nothing is wasted and there is no filler.

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 12-parameter mutation tool with no output schema, the description covers the action and the auth scope, and annotations cover the safety/idempotency profile. It still omits partial-vs-full update semantics and which fields are optional in practice, which an agent needs to call this correctly.

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% across 12 parameters, so the schema already documents id, notes, amount, status, dates, and the various foreign-key IDs. The description adds no parameter-level detail beyond confirming the ID is the identifier, so the baseline of 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 ('Update an existing purchase order by ID'), which is unambiguous and operationally precise. It doesn't explicitly differentiate from the many sibling update_* tools or explain how it relates to update_purchase_order_line, but the resource is clearly named.

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 gives no when-to-use guidance, no alternatives (e.g., update_purchase_order_line for line items), and no prerequisites beyond the scope requirement. The agent must infer that this tool edits an existing PO rather than creating one.

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