expiries_update

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

Annotations already establish that this is a non-destructive, idempotent mutation, so the bar is lower. The description still adds real behavioral context beyond them: changing `expiresAt` restarts the reminder schedule, `vehicleId: null` detaches rather than deletes, and `closed: true` suppresses creation of the next item.

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?

Three short clauses, all front-loaded after the one-line purpose statement. Every clause carries non-obvious information (reminders, detach, no successor item); nothing is wasted.

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 mutation tool with no output schema and annotations covering safety, the description covers the highest-risk side effects an agent could otherwise trigger accidentally. It does not state whether the update is partial (only supplied fields changed) or whether `kind` can be changed after creation, which keeps it short of full completeness.

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 moderate (58%), and the description supplies semantics the schema cannot: the reminder restart side effect of `expiresAt`, the detach meaning of a null `vehicleId`, and the manual-close meaning of `closed`. It leaves the remaining parameters (kind, label, notes, number, provider, companyId, validFrom, remindDaysBefore) entirely to the schema, so it is not exhaustive.

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 ("Update an expiry item"), which clearly separates it from expiries_create, expiries_delete and expiries_get. It does not name the closest sibling, expiries_renew, although the "without creating the next one" phrasing hints at the boundary.

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 only implied: the closing note contrasts manual closure with automatic renewal, so an agent can infer when to prefer this over expiries_renew. There is no explicit statement of when to use this tool versus the alternatives, nor any prerequisites.

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