Get what's playing

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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=false), and the description adds real context beyond them: the ADB prerequisite, that a missing setup produces an explicit error, that state is 'idle' when nothing plays, and that position_s is null for live TV. It stops short of describing latency, caching, or polling behavior, so it is strong but not exhaustive.

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?

The primary payload (what is reported) is front-loaded in the first sentence, with edge-case semantics and the prerequisite following in a tight second block. Every sentence carries information; nothing is redundant 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 no-argument, read-only probe with an output schema, the description covers everything an agent needs that the structured fields do not: the setup prerequisite, the failure mode, and the two non-obvious value semantics (idle state, null position for live TV). Nothing material is missing.

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 there is nothing for the description to disambiguate; per the baseline for a 0-parameter schema this lands at 4. The description correctly adds no parameter discussion and instead spends its words on return-value semantics.

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?

The description gives a specific verb and resource ('Report what is playing') and enumerates the exact fields returned (app, title, subtitle, play state, position in seconds), so the agent knows precisely what it gets back. It does not, however, differentiate itself from the sibling get_status, which could plausibly also report playback state.

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?

Usage is only implied: an agent can infer this is the tool for 'what's on right now,' and the idle/live-TV notes hint at when results are meaningful. There is no explicit statement of when to prefer this over get_status or how it relates to the other read-oriented siblings.

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