play_url

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

The description only states the action ('play') without revealing behavioral details beyond the annotation (readOnlyHint=false). It does not explain whether the stream replaces the current track, how errors are handled, or if any side effects occur (e.g., stopping other playbacks). The agent lacks critical context for safe invocation.

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 description is a single sentence that immediately communicates the tool's core function. It contains no filler or redundancies. All words are meaningful and earn their place.

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?

Given the tool's simplicity and the presence of full schema coverage, the description is adequate but not complete. It lacks context for when to choose this over siblings, and does not explain return values or behavior. A more complete description would include typical use cases and limitations.

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 schema already describes both parameters (playerId, url). The description adds no additional semantic meaning or constraints (e.g., supported URL formats, playerId resolution). Baseline score of 3 is appropriate as the schema carries the burden.

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 clearly states the tool's purpose: 'Play a direct URL or stream on a player'. It uses a specific verb (play) and resource (direct URL/stream), and distinguishes from sibling tools like play_radio_item or play_track which are for specific content types.

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 description provides no guidance on when to use this tool versus the many other play-related siblings (e.g., play_app_item, play_favorite). It does not mention prerequisites, such as that a player must be started or that the URL must be accessible. The absence of usage context makes it hard for an AI agent to choose this correctly.

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