add_to_library

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

There are no annotations, so the description carries the full burden. It does disclose a postcondition ('Saved playlists then appear in get_library_playlists') and ID formats, which is real value, but it says nothing about required permissions, whether the operation is idempotent, or what happens when all three optional string params are left at their empty defaults.

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 purpose and usage guidance are front-loaded in the first two sentences, and the Args block is short and scannable. The formatting is slightly redundant with the schema titles, but every line carries usable information about formats.

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?

An output schema exists, so return values need not be described, and the parameter formats are well covered. However, for a mutation tool with no annotations, the absence of any statement about permissions, failure modes, or the empty-input case leaves real gaps an agent would want before calling.

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?

With 0% schema description coverage, the description compensates well: it explains that song and album IDs are numeric and comma-separated, and that playlist IDs use the 'pl.' prefix. The one gap is that it does not say whether at least one ID group must be supplied, which matters for a tool where all three params are optional with empty-string defaults.

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: saving catalog songs, albums, or playlists into the user's library. It distinguishes itself from read siblings by naming the upstream sources (search_catalog, get_playlist_tracks, get_recommendations), though it never explicitly contrasts itself with add_tracks_to_playlist, which is the closest functional neighbor.

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?

Gives a clear trigger condition: 'Use this when the user wants to keep something found with search_catalog, get_playlist_tracks or get_recommendations.' It also states the downstream consequence (saved playlists appear in get_library_playlists). It lacks any explicit when-NOT-to-use guidance, particularly versus add_tracks_to_playlist.

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