Library stats

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower. The description still adds real behavioral context: enabling includeUserStats derives counts from watch history capped at the recent 10,000 plays, which is a data-scope caveat an agent could not get from the schema.

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 sentences, both front-loaded: the aggregate payload first, then the optional flag's effect and its data caveat. No filler and nothing repeated from the schema or annotations.

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 correctly enumerates what the response contains (totals, watched/unwatched, genre/decade/contentRating breakdowns) and explains the one non-obvious parameter. It falls short only on the 'user' and 'library' parameters, which remain unexplained.

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 only 33%: 'user' has a description, but 'library' and 'includeUserStats' have none. The description compensates well for includeUserStats (per-user play counts, 10,000-play window) but says nothing about the 'user' impersonation semantics or the 'Movies' default for 'library'.

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 stats for a library') and enumerates the exact aggregates returned (totals, watched/unwatched counts, genre/decade/contentRating breakdowns). This clearly separates it from listing siblings like list_libraries and list_media, though no sibling is named explicitly.

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?

Usage is implied by the word 'Aggregate' and the includeUserStats note, which tells the agent when to flip that flag. There is no explicit 'use this instead of X' routing or statement of when not to use it, leaving the agent to infer that this is the summary tool versus the enumeration tools.

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