ACTION_MEDIA_CONTROL

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

With no annotations, the description carries the full burden and does well: it discloses the Shizuku/root permission requirement, the output variables (media_success, media_error), and that results are returned as a variable-snapshot JSON. It omits what happens when no media session is active or how failures are reported beyond the error variable.

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 clauses, front-loaded with purpose then prerequisite then output/interpolation behavior. No filler, though the interpolation remark is dense shorthand an agent must parse.

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 4-optional-parameter, no-annotation, no-output-schema action, the description covers what it does, what it needs (Shizuku/root), what it returns, and templating support. Remaining gaps (no-active-session behavior, error semantics) are minor against a fully documented schema.

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 coverage is 100%, so the enum, defaults and per-parameter meanings are already documented in the schema. The description adds one genuine cross-cutting fact — string parameters support ${var} interpolation — but says nothing about cmd/require/on_error semantics beyond that, so baseline 3 fits.

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+resource: 'send media keys (play/pause/track skip, etc.) to the currently playing app'. The scope 'currently playing app' distinguishes it from siblings like ACTION_PLAY_MEDIA, ACTION_VOLUME or ACTION_GLOBAL_KEY without naming them explicitly.

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 a real prerequisite ('requires Shizuku or root'), which is useful context for selecting the tool. However it never says when to prefer this over ACTION_PLAY_MEDIA, ACTION_VOLUME, or ACTION_GLOBAL_KEY, and gives no exclusions or failure conditions.

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