list_devices

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuine context beyond them: the query is a server round-trip (not a local cache read) and it spells out the returned fields, which matters because no output schema exists.

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: what it does, the shape of the result, then when to use it. The routing hint to update_device/remove_device is front-loaded at the end where it is most actionable, and no sentence is 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 parameterless read tool with no output schema, the description supplies exactly what is missing: the origin of the data, the returned field names, and the semantics of the notable value (device id 1 is the primary phone). An agent can call this and interpret the response without further documentation.

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?

Zero parameters, so per the rubric this is a baseline 4. The description explicitly confirms 'Takes no parameters,' which is consistent with the empty schema and removes any doubt for the agent.

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 all devices linked to your Signal account') and adds the provenance detail that results come from Signal's servers rather than a local store. That scoping distinguishes it clearly from siblings like add_device, update_device, and remove_device.

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 names two use cases (audit device access, obtain a device id) and routes to the tools that consume that id: update_device for rename and remove_device for unlink. Nothing is left to inference about when to reach for this tool.

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