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

Annotations already declare destructiveHint=true, idempotentHint=false and openWorldHint=true, so the safety profile is covered. The description usefully reinforces this with 'sensitive write operation' and surfaces the confirm=true gate as a hard precondition, which is real behavioral value beyond the annotations — though it does not say what is overwritten or whether the change is reversible.

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 compact sentences, front-loaded with the action and endpoint, followed by the limitation. No filler, though the endpoint path is somewhat redundant with the tool's purpose.

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 12-parameter non-idempotent mutation with no output schema, the description covers the confirmation gate but says nothing about the other writable fields, partial-vs-full update semantics, or auth/workspace scoping. Adequate minimum, but real gaps remain.

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?

With 12 parameters and only ~50% schema description coverage, the description carries some burden but adds nothing about any parameter — not what fields like terms, qr_file, or payment_details do, nor that invoice_id is the target. The confirm requirement is the only parameter-adjacent detail, and that is already documented in the schema.

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 gives a specific verb+resource ('Updates an invoice') and even the exact endpoint, so an agent can distinguish it from get_invoice, delete_invoice, or mark_invoice_paid. It stops short of explicitly naming those siblings, but the update semantics are unambiguous.

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?

Usage is implied by the verb and a precondition is stated ('requires confirm=true'), which tells the agent this will fail without confirmation. However, there is no guidance on when to prefer this over mark_invoice_paid/mark_invoice_void or other invoice mutations.

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