list_spotify_devices

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

Annotations already establish readOnlyHint=true and openWorldHint=false, so the bar is lower, and the description still adds real value: it clarifies no audio session is created and that an empty result is not proof the TV is offline because the device may not advertise Spotify. That is a non-obvious failure-mode caveat an agent would otherwise misread. It omits auth/credential or enumeration-timing details, so not a 5.

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, no filler. The scope is front-loaded and the interpretive caveat about the empty list follows immediately as the single most important secondary fact.

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?

No output schema and no parameters, so the description carries the burden for return semantics, and it addresses the one trap that matters (empty list ≠ offline). It could have sketched what a discovered target looks like, but for a zero-argument read tool this is close to sufficient.

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, which is the baseline-4 case; there are no arguments whose meaning could be lost. The description correctly does not waste words restating the empty schema.

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?

Uses a concrete verb ('Discover') plus a specific resource ('current Spotify Connect targets') and rules out the adjacent write behaviours (starting or transferring audio), which separates it from control_spotify. It stops short of naming that sibling, so an agent must infer the pairing rather than being told directly.

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?

The 'without starting or transferring audio' clause implies this is the read-only inspection call and that playback should go through a sibling, but no explicit when-to-use or when-not-to-use condition or alternative tool is named. Usage is inferable rather than stated.

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