invoices_cancel

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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false, so the description does not need to restate that this mutates. It does add real context beyond annotations: the status transition to 'cancelled' and the fact that the record is retained rather than purged, which is exactly what an agent needs to judge consequences.

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?

Four short sentences, front-loaded with the action and the required input, then the resulting state, then the recovery path. Nothing is redundant or padding.

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?

Given a mutation tool with full annotation coverage, a complete parameter schema and no output schema, this is nearly sufficient: the agent knows the required input, the state change and how to undo. Minor gaps remain around permissions or restrictions on which invoice states can be cancelled (e.g., paid or already-issued invoices).

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%, so the uuid, reason and companyId parameters are already documented in the schema. The description only repeats the reason minimum length, adding no syntax, format or edge-case meaning beyond the structured fields; baseline 3 applies.

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 ('Cancel an issued invoice') and immediately distinguishes the effect (status becomes 'cancelled', record retained) from deletion. It also names the sibling that reverses the action, so the agent can separate it from invoices_delete, invoices_bulk_cancel and invoices_storno.

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?

Explicitly routes accidental cancellations to invoices_restore, which is a concrete alternative condition. It does not, however, say when to prefer this over invoices_delete, invoices_storno or invoices_bulk_cancel, so the sibling routing is only partial.

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