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

Annotations only declare write/non-destructive/non-idempotent, and the description adds substantial behavior beyond that: no fire_at yields an immediate notification, fire_at yields a reminder, and urgent alarms ring through silent mode and Focus until Done or Snooze — a real side effect an agent must know before calling. It also flags the tool's legacy status, which is behavioral context nothing else carries.

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-loaded with the core mode split, and the color/sound/icon advice is compressed into pointers ("see the sound argument") rather than repeating the enum text. Still somewhat long for a create tool, with a few sentences that restate schema-documented defaults, but nothing is wasted outright.

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 10 optional parameters, no output schema, and annotations covering only the safety profile, the description carries the load well: it covers both execution modes, urgency semantics, silence/Focus behavior, and guidance for the optional presentation fields. An agent has everything needed to call it correctly without opening the schema.

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; the description still adds cross-parameter policy the schema documents only field-by-field — that sound applies only to urgent ringing alarms and that fire_at should be supplied only when the user named a time. It does not add format details for fire_at/ends_at/countdown beyond the schema, so it stops 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?

States a specific verb and resource ("Create an alarm on the user's iPhone") and immediately splits the behavior into the two modes an agent must choose between: notification now vs. reminder at fire_at. The "legacy / kept for agents set up before 2026-10" note signals it may be superseded, but it never names the replacement or explains how it differs from the sibling tool `alert`, so differentiation is incomplete.

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 strong, explicit when-to-use rules: "Use urgent only when the user must not miss it," plus a phrase-to-intent mapping ("call me", "ring me", "wake me" in any language → urgent alarm). It also says when to omit color and sound. It never routes the agent among siblings (create vs. update_alarm vs. alert), so the alternatives half of the guidance is missing.

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