saved_runtime_by_era

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

With no annotations provided, the description carries the full behavioral burden, and the explicit 'Read-only' tag is a genuine safety disclosure beyond what the name conveys — the most important trait an agent needs before invoking. However, it discloses nothing else: no implication of scanning up to 10,000 paginated saved items, no cost or quota considerations, and no behavior at scan limits. It covers the safety profile but not the operational behavior.

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 description consists of one front-loaded sentence stating the core aggregation plus a two-word safety qualifier 'Read-only.' With the title null, this is the only textual definition, and there is zero waste — every word earns its place.

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?

The description explains the core computation and the schema fully documents all parameters, making the tool safely invokable in isolation. However, with no output schema, it doesn't indicate the shape of the returned per-decade breakdown, and it gives no selection context among the large field of era/reporting siblings. Adequate for invocation but incomplete for confident tool choice.

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%, and the schema already documents all three parameters with defaults (scancap, max_results, response_format), so the baseline of 3 applies. The tool description itself adds no parameter-level meaning beyond what the input schema provides, which is acceptable because coverage is complete.

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 states a precise aggregation — total listening runtime of saved tracks grouped by release decade of each track's album — which clearly identifies the tool's computation and resource. The phrasing is unambiguous and distinguishes it from siblings like saved_tracks_by_artist (grouped by artist) and saved_albums_by_decade (albums, not track runtime), though it doesn't explicitly name any alternatives. The verb is implied rather than explicit, but the noun phrase carries full clarity.

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 offers no guidance on when to use this tool relative to the many overlapping analytical siblings (saved_tracks_by_artist, era_distribution_report, era_preference_report, playlist_era_profile, album_duration_report). No prerequisites, exclusions, or alternative-selection conditions are stated, so the agent must infer usage context from the name and subject matter alone. This is 'no guidance' rather than misleading guidance, hence a 2.

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