add_current_to_playlist

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

Annotations already declare readOnlyHint=false and destructiveHint=false, so the safety profile is partly covered. The description adds genuinely useful behavioral context beyond that: 'Skipped if already there' discloses idempotency and 'Changes the user's library' discloses a persistent side effect.

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?

Four short, front-loaded fragments with virtually no waste. The negation that supports idempotency is stated explicitly and the essential information leads.

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?

For a two-parameter mutation tool with no output schema and annotations covering safety, the description supplies the key missing facts: what track is added, that it is idempotent, and that the library changes. Details like which playlist scope (owned vs followed) are left implicit.

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 both parameters (playlist and create_if_missing) are already documented in the schema. The description's 'Needs playlist' merely restates the required field and adds no format or behavior detail beyond the schema.

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: 'Add the playing track to one of the user's playlists.' The phrase 'the playing track' implicitly distinguishes it from the sibling add_to_playlist, which takes an explicit track argument, but no sibling is named outright.

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 only implied by 'the playing track' — the agent can infer this is for the currently playing item rather than a specified track. There is no explicit statement of when to prefer this over add_to_playlist, add_to_queue, or save_tracks.

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