library_info

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

With no annotations, the description carries the full behavioral burden. It explicitly discloses that it scans all tracks and is fast, and the word 'Summarise' implies a read-only operation. It does not belabor safety caveats, which is acceptable for a summary endpoint; the added performance/scope context goes beyond a mere tautology.

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 first sentence front-loads the tool's purpose and compresses the output list into a semicolon-separated enumeration without fluff. The second sentence adds a valuable performance clue. Every word earns its place, and the structure is easy for an agent to parse.

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 that an output schema exists, the description need not spell out return structures. It provides the essential context for a zero-parameter tool: what it summarizes, the scope (whole library), and performance ('fast'). An agent can correctly select and invoke this tool with no missing information.

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?

The tool takes zero parameters and the input schema is empty, so schema coverage is trivially 100%. The description cannot add parameter-level meaning beyond the schema, and per the zero-parameter baseline this is properly scored as 4.

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 'Summarise the whole library in one call' and then enumerates the exact aggregated outputs (track totals, bpm/key/energy counts, key notation, playlist counts, tag categories/tags). This is a specific verb+resource statement that clearly differentiates it from siblings like list_playlists or get_track, which target narrower slices.

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 gives clear context: this is the one-call whole-library summary, 'fast' and scanning all tracks. It implies the agent should use it when an overview of the entire library is needed rather than specific tracks/playlists, but it does not explicitly name alternative tools or state when-not-to-use, so it falls just short of a 5.

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