List devices

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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so safety is covered. The description adds context beyond that: it is a single Garmin request, and critically it discloses a limitation (the last-used device is not shown), which prevents a wrong default assumption. A minor gap is that 'one Garmin request' hints at quota but doesn't state any rate limit.

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 what is listed, then the usage rule, then the operational cost. Every sentence carries distinct information with no padding.

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 zero-parameter, read-only listing tool with an output schema present, the definition supplies everything needed: what is returned, why to call it, what it omits, and its cost profile.

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?

The tool takes zero parameters, so the baseline is 4. The description nonetheless maps the output field device_id to its downstream consumer (push_workout_to_device), which adds meaning that the empty input schema cannot carry.

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 ('List the Garmin devices paired with the account') and enumerates the returned fields (device_id, name, product, primary activity tracker). An agent can tell this apart from siblings like list_activities or garmin_status immediately.

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 tells the agent when to use this: to obtain the device_id that push_workout_to_device requires. It also names the consequence of skipping it (a push without device_id prefers the last-used device, which this list does not reveal), which is a precise when/when-not rule.

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