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 mutation profile is covered. The description adds genuinely useful behavior beyond that: partial-replace semantics per day, empty-list-closes-a-day, and the rule that a booking must fit entirely inside one window, which determines how windows behave.

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 sentences, front-loaded with the core replace semantics followed by the slot-building consequence. The worked 08:00–10:00 / 10:30–12:30 example is compact and directly actionable, and nothing is redundant.

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 destructive mutation with no output schema, the description covers the essential semantics: partial update scope, closure behavior, and window/booking interaction. It omits what happens to already-booked appointments when hours are replaced, which an agent would want given destructiveHint=true.

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 0% schema description coverage and nested objects involved, the description must carry the load, and it does: it explains the semantics of `days` (leaving one out leaves it unchanged) and `windows` (empty = closed), plus the booking-fit constraint that governs window values. It lacks detail on locationId and on how openTime/closeTime pairs relate to each other, keeping it short of a 5.

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 first clause gives a precise verb+resource+scope: 'Replace a location's hours for the listed days.' An agent can distinguish this from siblings like add_closed_dates (closures) and update_location_settings without opening either 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?

The description clearly states the operating context: omitted days are unchanged and an empty windows list closes a day, plus a worked example of how to produce fixed slots. It does not name explicit alternative tools (e.g. add_closed_dates for one-off closures), so it stops short of full when/when-not routing.

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