library_genre_report

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

Annotations already declare readOnlyHint and idempotentHint, so safety is covered. The description adds real behavioral context: it scans the entire saved library (not a filtered subset), performs an artist-level join against the tag sidecar, and returns counts plus contributing artists, with an explicit coverage limitation. It stops short of describing pagination or how max_results truncation affects the aggregates.

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?

Three sentences, all front-loaded with the operation first, then mechanism, then the important data-availability caveat. Every sentence earns its place with no redundancy.

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?

With no output schema, the description does the work of explaining the return shape (per-genre track/album counts plus contributing artists) and the crucial limitation that untagged artists are excluded. It is nearly complete; only the effect of result truncation on the aggregates is left implicit.

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 max_results and response_format are already fully documented in the schema, including the enum values and default. The description adds nothing about either parameter, so the baseline of 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?

States a specific verb and resource ('Aggregate your saved library by user-declared genre tags') and explains the mechanism: scanning saved tracks/albums and joining artists against the tag sidecar. This clearly distinguishes it from siblings like filter_by_genre, tag_management, and library_hygiene without needing to open any schema.

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 strong contextual guidance: it points to tag_management for the sidecar and warns that only tagged artists appear because Spotify exposes no genre data. That tells the agent when output will be useful, but it never explicitly states when to prefer this over alternatives such as filter_by_genre or a plain saved-tracks listing.

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