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

With annotations only declaring readOnlyHint=false, openWorldHint=true and destructiveHint=false, the description discloses substantial behavior beyond them: state persistence (stays Unfinished, editable, not counted in tax reports), generated invoice number, calculation of due date from payment terms, returned totals, and the auth/confirmation requirements. This is exactly the extra context a mutation tool needs.

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?

Dense but front-loaded, with the most important fact (what state the invoice lands in) first. Sentences are short and each carries distinct information, though the confirmation/auth remarks could be slightly tighter.

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?

Even though there is no output schema, the description explains the returned values (net, VAT, gross totals, due date), the resulting record state, and the auth/confirmation prerequisites. Nothing an agent needs in order to call it correctly is missing.

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 four parameters are already documented (partner_id from list_partners, rows structure, date default, additional_info placement). The description adds no parameter-level semantics beyond the schema, so the baseline of 3 is appropriate.

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 ('Save a sales invoice as Unfinished') and clarifies the scope by distinguishing it from sending/approving via the sibling tools. The 'return the totals' phrase adds what the call yields in one line, so an agent can identify it without opening the schema.

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 clarifies context ('Creates the invoice the way Save does in Invoice view', 'stays Unfinished: editable, not sent') which implies you must use a sibling such as procountor_send_sales_invoice to actually send it, but it never names alternatives explicitly. It does add confirmation guidance ('confirm with the user before each call'), which is useful usage context.

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