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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description is free to add genuinely new behavior: the error returned for an id that isn't the person's alarm, the point-in-time ('as it is now') semantics, and the MCP Apps card rendering. It does not mention rate limits or pagination, but neither is relevant for a single-record fetch.

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 tight sentences, front-loaded with the core verb+resource, then constraints, then return shape. Every clause carries information an agent needs; nothing is redundant with the title.

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 compensates by enumerating the returned fields (name, type, reach, on/off, next ring, link) and disclosing the error case for foreign ids. Combined with annotations, an agent has everything needed to call and interpret this tool.

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 the single uuid parameter is fully specified by the schema, including format and pattern. The description reinforces that the id must belong to the person's alarms but adds no syntax or format detail beyond the schema, so 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?

States a specific verb and resource ('Shows one of the person's alarms by its id') plus the exact scope of what is returned, and explicitly separates itself from listing/searching siblings. An agent can distinguish it from list_my_alarms or update_alarm without opening any 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?

Gives clear usage context (requires an id) and an explicit exclusion ('it does not search by name or list alarms'), which steers the agent away from misuse. It stops short of naming the alternative tool (e.g. list_my_alarms) as the way to obtain an id, so it is clear but not fully routing.

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