playlist_union_preview

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 handles it well: it explicitly declares read-only/no-writes, discloses the quota cost (🟢 N GETs), and reveals ordering semantics (first-seen) which implies deduplication behavior. It does not cover truncation interactions with max_results or exact count semantics, but the key safety and cost traits an agent needs are stated.

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 tight sentences with zero filler. The core purpose, ordering behavior, output contents, safety guarantee, and quota cost are each delivered in a compact, front-loaded format. Every clause 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?

Despite having no output schema and no annotations, the description conveys the output shape (ordered sequence, per-playlist counts, unique-to-each counts) and the safety profile, while the schema fully documents parameters. The only notable gap is not mentioning pagination/truncation semantics for max_results relative to the counts, but for a low-complexity preview tool this is minor.

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%, with all three parameters (playlist_ids, max_results, response_format) already well documented in the schema including defaults, bounds, and enum meanings. The tool description adds no parameter-specific semantics beyond restating the 2–10 playlist bound already present in the schema, so the baseline of 3 applies.

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 names a specific verb ('Preview'), a specific resource (the union of 2–10 playlists), and precise behavioral detail ('first-seen-ordered sequence, with per-playlist counts and how many tracks are unique to each'). This clearly differentiates it from siblings like playlist_intersect, playlist_subtract, and especially playlist_union, which is the write counterpart.

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 'Preview' framing plus the explicit 'read-only, no writes' declaration makes the usage context clear: use this to inspect a union result without committing changes. However, it does not explicitly name the alternative (playlist_union) or state the condition for choosing between them, leaving that routing to inference from the name and sibling list.

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