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

Annotations declare the safety profile (readOnlyHint=false, destructiveHint=false), and the description adds substantial context beyond that: exactly what is copied (customer, line items, currency, notes, payment methods, tax-inclusive setting), what is reset (no dates or invoice number), that the original is unchanged, and that nothing is sent.

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?

Front-loaded with the core action and result, followed by copy semantics and workflow routing. Three sentences, all of which earn their place with no filler.

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?

No output schema exists, and the description still states what is returned (the draft with its id). For a two-parameter duplication tool, the description covers action, side effects, non-effects, and next steps completely.

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 coverage is 100%, so both id and companyId are already documented. The description reinforces company scoping ('the copy is always created in that company') and the 'any status' property of the source invoice, but adds little beyond the schema's own parameter descriptions.

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 (copy/duplicate) and resource (sales invoice) with precise scope: creates a new draft in the same company and returns its id. It explicitly distinguishes itself from create-invoice-draft, so an agent can differentiate without opening either 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?

Names the alternative (create-invoice-draft for an empty draft) and the follow-on tools (update-invoice-draft to set dates, submit-invoice to finalize), giving explicit when-to-use routing and workflow sequencing.

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