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 known. The description adds real value beyond that: the PDF is deleted along with the record, the action is permanent and cannot be undone, and user confirmation should precede the call. It does not mention permissions or effects on related data such as payments.

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 short sentences, front-loaded with the action and its scope, then the prerequisite, then the safety warning. Every sentence carries distinct, actionable information with no repetition of the title or annotations.

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 three-parameter destructive tool with no output schema, the description covers scope, prerequisites, and irreversibility well enough to call it safely. The only gap is whether deletion cascades to related records such as payments or estimates, which an agent might want to warn the user about.

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 three parameters including the required id and the two display-only fields are already documented in the schema. The description only reinforces that id comes from list_invoices; customerName and invoiceNumber are not discussed, 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 ('Permanently delete an invoice') plus the notable scope detail that its PDF is removed too. This clearly separates it from fetch_invoice, update_invoice, and the other delete_* siblings, which operate on different resources.

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?

Gives an explicit prerequisite ('Requires the invoice ID') and routes the agent to list_invoices to obtain it, plus a confirmation step with the user before calling. It does not spell out when not to use it, but for an irreversible delete the intended usage is unambiguous.

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