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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds one genuinely new behavioral fact — 'one task covers every brain' (scope of the registration) — and reinforces idempotency with 'or the existing task when one is already registered', which largely restates the annotation rather than extending it.

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 short sentences with no filler, and the primary return behavior is front-loaded. Slightly awkward run-on phrasing ('...client scheduler, or the existing task when one is already registered') but no wasted verbiage.

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?

With no output schema, the description does explain what comes back (schedule + task prompt), which is helpful. However, it omits how this relates to schedule_get/schedule_set, whether calling it mutates any scheduler state, and what the agent should do with the returned prompt — gaps that matter for a 0-required-param tool whose name implies a write.

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 description coverage is 100% and both parameters (hour with a documented default of 7, and IANA timezone) are fully described in the schema. The description adds nothing about parameter meaning or interplay, so the baseline 3 applies.

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 description does state a concrete outcome — returning a recommended daily schedule plus a suggested task prompt, or the already-registered task — but the verb 'returns' sits awkwardly against the tool name 'register', leaving it unclear whether this is a read or a registration action. It also never distinguishes itself from the closely named siblings schedule_get and schedule_set.

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?

There is no when-to-use guidance, no prerequisites, and no mention of the obvious alternatives schedule_get and schedule_set. An agent cannot tell from this text why it would call schedule_register rather than schedule_get when it just wants to inspect the current schedule.

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