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

With no annotations, the description carries the full burden and does disclose the most important trait — a destructive overwrite ('replacing what was there'). It also documents the empty-list edge case. It omits permission/authorization requirements and whether omitted person_id defaults to the caller.

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 sentences, front-loaded with the action and overwrite warning, followed by format and edge-case detail. No 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?

For a 3-param tool with no annotations and no output schema, the description covers the destructive semantics, value formats, and empty-list behavior. Remaining gaps are person_id handling and validation limits (maxItems 28), which are minor but real.

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 0%, so the description must compensate; it explains the nested hours array semantics (weekday 0=Sunday..6, HH:MM in shop-local time) and the empty-list meaning, which the schema cannot convey. However, the optional person_id parameter is never mentioned, leaving the agent unsure whose hours are set when it is omitted.

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 with scope: 'Set a worker's weekly hours', which distinguishes it from the shop-level sibling schedule_setShopHours and from the additive availability_addTimeOff/removeTimeOff. The replace-vs-add semantics are explicit.

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?

Clear context is given: this replaces existing hours, and an empty list clears them to always-available. That tells the agent when to use it for wholesale rewrites, but it never names an alternative for partial edits (e.g., addTimeOff) or states when not to call it.

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