play_youtube

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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=false, so the agent knows this is a non-destructive local-network action. The description adds one useful behavioral detail, that a t= start time is honored, but does not disclose what happens to currently playing content or any failure modes.

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?

A single front-loaded sentence with no filler; the purpose comes first and the start-time caveat is a brief trailing clause.

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?

An output schema exists, so return values need not be documented, and annotations cover the safety profile. The only real gap is prerequisite/alternative routing (paired TV, launch_app overlap), which is minor for a two-parameter tool.

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% and both parameters are described there (tv default behavior, accepted URL forms and 11-char id). The description's 't= start time' clause adds a small amount of meaning beyond the schema, matching the baseline-3 case where the schema does the heavy lifting.

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: 'Play a YouTube video on the TV', which is meaningfully distinct from the generic launch_app sibling. It also notes the t= start-time handling. It does not explicitly name which sibling it should be preferred over, so it stops short of the top score.

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 implied by the purpose text but there is no explicit when-to-use guidance, no exclusion for launch_app (which could also open YouTube), and no mention of prerequisites such as a paired TV being required.

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