Label the library's moods

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

No annotations are provided, so the description carries the full burden. It discloses the one-time permanent caching, the scope ('every track'), and the check-vs-run modes, plus why it cannot rely on existing metadata. However, it doesn't state the return format or authorization requirements, and the mutation is not explicitly flagged as a write, though 'cached permanently' implies persistent side effects.

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 paragraphs; the first states the core purpose and outputs, the second provides rationale and persistence behavior. Every sentence adds value, though the first sentence is long and packed with attributes, making it slightly dense.

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 tool with no output schema, the description explains the tool's role, prerequisites, caching, and the two modes (run/check), which covers the key behavior. It doesn't specify what a successful run returns (e.g., coverage counts), but the schema's status_only parameter hints at that.

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 documents both parameters. The description reinforces the semantics by mentioning 'check' for status_only and 'trial run' for limit, but adds no new parameter-specific details beyond what the schema provides.

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 identifies the action ('Run (or check)') and the resource ('one-time pass that gives EVERY track a mood'), enumerating the specific mood attributes. It distinguishes from sibling tools by explaining it enables library-wide mood search, unlike playlist-scoped capabilities.

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 provides clear context on when to use: to enable mood search across the whole library, and explains why existing metadata is insufficient (genres are coarse, BPM/ReplayGain/MusicBrainz IDs under 3%). It doesn't explicitly name alternatives but implicitly differentiates from playlist-only operations and mentions the caching behavior for 'runs once'.

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