get_play_url

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

No annotations are provided, so the description carries the full behavioral burden. It discloses the most important trait — no playback is triggered, only a URL is returned — which implies a side-effect-free read. However, it does not disclose failure behavior, URL expiration, or ambiguous-query handling, which are meaningful gaps for a network-backed resolver.

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?

Two dense sentences with zero filler: the first states the purpose, the second gives the usage condition and the behavioral contrast. Every clause earns its place, and the core fact is front-loaded.

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 3-parameter tool with full schema coverage and no output schema, the description supplies the essential contract: what it resolves, when to call it, and what it returns (an address, not playback). It falls just short of describing the return format or how resolution differs when song_id is provided versus a text query.

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%, so the schema already documents all three parameters. The cross-reference '参数与 play_song 相同' adds no new semantic detail beyond what the schema provides. Baseline 3 applies because the description neither needs to nor does compensate for any coverage gap.

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 opens with a specific verb+resource: '解析歌曲的直链播放地址' (resolve a song's direct playback URL), which states exactly what the tool produces. It also distinguishes itself from siblings with '只返回地址不播放' (only returns the address, doesn't play), cleanly separating it from play_song even though both share the same parameter set.

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?

It gives an explicit trigger condition: '当其他工具需要具体音频 URL 时使用' (use when other tools need a concrete audio URL). The contrast with play_song is implied via '参数与 play_song 相同，只返回地址不播放', but it stops short of naming explicit when-not-to-use scenarios or other alternatives among the siblings.

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