Mark an invoice uncollectible (it can still be paid)

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

Annotations already declare destructiveHint=true, readOnlyHint=false, idempotentHint=false, so the write/destructive profile is covered structurally. The description adds genuinely useful context the annotations cannot convey: the invoice remains payable, meaning this is a bookkeeping designation rather than a cancellation. It still omits whether the action can be reversed or un-marked, and what happens to an invoice that is already paid or already uncollectible.

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?

Short and front-loaded, with the key caveat (still payable) stated immediately. The cost is repetition: the first line restates the title verbatim, and "the customer can still pay it" says the same thing as the parenthetical, so two of the three sentences carry overlapping 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?

For a one-parameter mutation with no output schema, the definition covers what it does and one important semantic nuance. It falls short on reversibility and on sibling disambiguation versus void_invoice — the two things an agent most needs to choose and 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% for the single parameter, and the schema documents the `inv_…` id format. The description adds nothing about the id parameter, so the baseline of 3 applies — the schema carries the burden and does it adequately.

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 ("Mark an open invoice uncollectible") and scopes it to open invoices. It never names a sibling such as void_invoice or update_invoice, so the boundary between this and voiding an invoice is left implicit — the parenthetical about the customer still being able to pay hints at the difference but does not draw it.

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 word "open" implies a precondition (only open invoices qualify) and the note that the customer can still pay implies a when-to-use context — for record-keeping/write-off rather than cancelling the debt. However there is no explicit statement of when to prefer this over void_invoice, nor what happens if the invoice isn't open.

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