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

Annotations cover the safety profile (destructive/idempotent/not read-only), and the description adds context annotations cannot express: partial-replace semantics, the invariant that a booking must fit inside a single window, the return value ('full location setup'), and the required scope/role (locations:write, Admin).

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-loads the core replace behavior, then usage guidance, the alternative tool, return value, and auth requirement in a logical order with no filler. The fixed-slot example is dense but earns its place by clarifying a non-obvious window-sizing rule.

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 mutation tool with nested params, no output schema, and annotations covering safety, the description supplies everything else an agent needs: replace scope, window invariants, alternative tool, return value, and auth requirement.

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 the baseline is 3, but the description goes further by interpreting the windows/day semantics (empty list closes the day, window length constrains bookable slots) in a way the schema field descriptions alone do not convey. It does not add syntax details beyond what the schema already specifies.

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 ('Replace a location's hours for the listed days') and immediately clarifies replace semantics (omitted days unchanged, empty windows closes a day). It also distinguishes itself from the sibling add_closed_dates, so an agent can separate these 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?

Explicitly routes one-off closures to add_closed_dates, and gives a concrete pattern for producing fixed slots via one-appointment-long windows. Both the when-to-use and the when-to-use-something-else conditions are stated, not inferred.

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