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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false, so the safety profile is covered. The description contributes the auth requirement ('Requires purchase_orders:write scope'), which is genuinely useful, but says nothing about whether omitted fields are preserved or cleared and gives no warning about the destructive nature beyond the annotation.

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 action and followed by the permission requirement. No redundant restatement of the title or name.

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 with no output schema, the description covers identity and auth but omits the behavior an agent most needs: whether the call is a partial or full update and what happens to fields left unspecified. Adequate but with a clear gap.

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 all 12 parameters are documented in the schema and the baseline is 3. The description adds only that updates are keyed by ID, which is already implied by the required 'id' property; it adds no partial-update semantics.

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+resource ('Update an existing purchase order by ID'), so the agent knows exactly which entity is mutated. However, in a sibling set containing update_purchase_order_line and update_purchase_order_link, it never distinguishes itself from those near-neighbors.

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?

'by ID' implies an existing record is required, but there is no guidance on when to choose this over bulk_update, update_purchase_order_line, or create_purchase_order. No prerequisites or exclusions are stated.

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