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

With no annotations, the description carries the burden and does disclose key behavior: the lines are *replaced* (destructive, not appended), the effect is deferred to the next term's invoice, and already-issued invoices are unaffected. The parenthetical '(owner or office; you write them, never AI)' also signals that the agent must not invent prices — an unusual but real guardrail. Missing are permission requirements, whether the operation is reversible, and failure modes.

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 dense sentences with the replacement scope front-loaded and the invoice-timing caveat second. No wasted prose; the parenthetical is slightly cryptic in phrasing but carries an actual constraint rather than 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?

Full as described.

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 only 33%, but the description adds the crucial semantic the schema lacks: 'lines' is a full replacement of the plan's priced lines, not an append. It also flags tax_rate_id as optional, though that is already documented in the schema. It adds nothing about the line item fields themselves (quantity, unit_price_minor as minor units, the 200-item cap) or the uuid format of plan_id.

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: replacing a plan's priced lines and optionally its tax rate. The scope (existing plan, keyed by plan_id) clearly distinguishes it from maintenance_createPlan, maintenance_getPlan and maintenance_cancelPlan, so an agent can select it without opening a 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?

Gives a useful timing boundary (applies from the next term's invoice; existing invoices keep their price), which tells the agent the call is not retroactive. However, it never names an alternative or a when-not condition — e.g. how this relates to maintenance_createPlan or pricebook tools — so the agent must infer that this is only for plans that already exist.

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