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

Beyond the annotations (destructiveHint/readOnlyHint already flag a mutating call), the description explains the nature of the effect: 'Off makes the screen dark until it is turned on again' and 'the player keeps running either way'. It also discloses the required permission (`screen.edit`) and that unauthorized screens are silently skipped in bulk calls, which annotations cannot convey.

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?

Five tight sentences, front-loaded with the core action and scope, then consequences, then the alternative tool, then the permission requirement. No filler or redundant restatement of the name.

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?

With annotations covering safety traits and an output schema covering return values, the description fills the remaining gaps an agent needs: effect duration, player-side impact, CEC limitation, bulk skip behavior, and the `screen.edit` requirement.

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 description coverage is 100%, with power's enum and both screenId/screenIds already documented in the schema. The description confirms the bulk semantics of screenIds but adds no format, limits, or edge cases beyond what the schema provides, so the baseline of 3 applies.

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 concrete verb (turn on/off) and resource (the TV attached to a screen) plus the transport mechanism (HDMI-CEC) and the single/bulk scope. It explicitly distinguishes itself from reboot_screen, so an agent can separate the two without opening either schema.

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?

Names the alternative tool and the condition that selects it ('To restart the player instead use reboot_screen'), states the environmental precondition (TV must accept HDMI-CEC), and documents bulk-call behavior for out-of-reach screens. This is explicit when/when-not guidance.

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