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

Annotations only classify this as a non-read-only, non-idempotent write; the description adds the non-obvious business rule that post-seal dates are refused and names the remediation path (accept_invoice_change applying a move_due_date suggestion). It stops short of 5 because it doesn't clarify whether re-setting the same date on a sealed invoice is permitted or what error/return signals the refusal.

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 tight sentences with zero filler; the operation and its value format come first, and the sealed-invoice constraint with its remediation follows immediately. Every clause carries information.

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?

With an output schema present, return values need not be described, and annotations cover the safety profile. The remaining functional gaps are minor: no explicit precondition (draft/unsealed state) and no statement of what happens on a redundant same-date set.

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 0%, so the description must carry the load. It does supply human-readable semantics for dueOn ('calendar day', YYYY-MM-DD) beyond the raw regex pattern, though it adds nothing about invoiceId beyond the self-evident name.

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?

The description states a specific verb and resource ('Set the due date') plus the value domain ('calendar day in YYYY-MM-DD form'), and it situates the tool relative to the sibling that owns the post-seal path (accept_invoice_change with move_due_date). An agent can distinguish it from suggest_invoice_change / accept_invoice_change without opening any 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?

It gives a clear when-not condition: once the invoice is sealed, a different date is refused and the change-suggestion route must be used instead. It does not explicitly state the normal precondition (invoice not yet sealed) or name suggest_invoice_change as the pre-seal alternative, so it stops short of full when/when-not/alternatives coverage.

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