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

Goes well beyond the sparse annotations: it discloses the accounting effect (keeps its number, leaves the books and the contact's balance), the two-step confirmation gate, the exact refusal token (`confirm-required`) and that the refusal describes what would have happened, plus not-found behavior for missing or foreign ids. This is exactly the disclosure an agent needs before mutating financial records.

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 operation and inverse, then the side effect, then the confirm protocol, then the error case — a sensible ordering. It is dense but every clause carries information; the slightly telegraphic phrasing costs a little readability.

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, yet the description covers the meaningful return states (confirm-required refusal with a description of the pending change, not-found) and the side effects of the mutation. Nothing critical is missing for correct invocation.

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 baseline is 3, but the description adds real meaning the schema lacks: the consequence of `void false` (un-void), the exact protocol for `confirm` including the refusal code, and that a foreign id yields not-found. That is value beyond the field 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 (void/un-void) on a specific resource (document) and enumerates the document kinds covered (invoice, quote, credit note, bill). It also immediately clarifies the inverse operation via `void false`, so an agent knows the full scope of the tool from one sentence.

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 a clear procedural rule: without `confirm true` nothing changes, ask the user, then call again with `confirm true`. It also implies the void-vs-delete distinction by saying a voided document 'keeps its number' while leaving the books. It stops short of naming `delete_document` as the explicit alternative, so routing between the two must be inferred.

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