save_to_library

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

No annotations provided, so description carries the burden. It discloses mutation (save to library), but not whether saves are idempotent, what happens with already-saved items (errors/ignored), authorization scope needed, or rate limits. dry_run description is in schema param, not description. Behavioral traits beyond annotations are absent.

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, no wasted words. Front-loaded with 'Preferred' and the URI mix. The dry_run note is useful and early. However, 'via Spotify's unified library endpoint' is mildly redundant with the rest of the sentence.

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 is adequate for a simple save call with 3 params and no output schema, but it omits error behavior for already-saved items and required auth scope. Given the operation is a mutation and among many save-related siblings, a bit more voice on difference vs save_items or save_episode would make it complete.

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 baseline 3. The description adds the contextual 'widest URI mix' and max 40 — max 40 already in schema. dry_run semantics is described in schema, not in description. Little added value, but not missing.

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?

Description states specific verb 'Save' + resource 'user's library' via 'unified library endpoint'. Notes max 40 and dry_run. However, it doesn't differentiate from siblings like save_items, remove_saved_items, save_episode, playlist_to_library, library_to_playlist which also involve saving/library actions. It claims 'Preferred' which implies distinction but doesn't say preferred over which alternative.

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 says 'Preferred' and 'Accepts the widest URI mix' in one request, implying it should be used ahead of narrower save tools. There is some guidance via 'dry_run=true to preview' for testing. But it doesn't explicitly state when not to use, nor name any sibling alternatives (e.g., check_saved_items before calling, or save_episode for shows/episodes). It does provide a clear use context: user wants to save mixed item types.

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