Cast URL

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

The description adds meaningful behavior beyond the annotations: the URL is signed, expires after 12 hours, and fetching it counts as a play for the account. This explains why readOnlyHint is false and gives the agent important side-effect context, though it omits auth requirements or rate-limit details.

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 compact sentence with no wasted wording, and the most important behavioral detail, the play-count side effect, is included alongside the return value and validity period.

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 simple two-parameter tool with complete schema coverage and no output schema, the description explains the return value, its validity window, and the important side effect. Nothing essential for correct invocation appears to be 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?

Schema description coverage is 100%, and both required parameters are fully documented in the input schema. The description does not add parameter-level meaning beyond what the schema already provides, so the baseline 3 is appropriate.

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 states a specific resource and return type: a signed MP3 URL of a track for a cast receiver. It is clear what the tool provides, though it does not explicitly distinguish itself from nearby siblings such as get_track, get_track_part, or streaming_quality.

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 phrase 'for a cast receiver' gives clear usage context, and the 12-hour validity plus play-count side effect help an agent understand when this is appropriate. However, it does not explicitly state when not to use it or name alternatives for ordinary playback or track metadata.

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