refresh_library

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

With no annotations, the description carries the full burden and does so well: it discloses the ~20s build cost, that the result is cached and reused, and that the effect is only otherwise visible after a cache TTL. It also clarifies the incremental freshness rule (likes immediate, playlist adds deferred), which is non-obvious and directly affects whether the agent should call it.

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 action is front-loaded in the first sentence and each subsequent sentence adds real information (cost, cache semantics, call condition). The cache-economics paragraph is slightly more expansive than strictly needed, but it is not wasted.

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. For a zero-parameter maintenance tool, the description covers the why, the cost, the caching model, and the precise call condition, leaving no material gap for an agent deciding whether to invoke it.

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?

There are zero parameters, so the baseline is 4 and there is no parameter syntax for the description to clarify. Nothing is missing, but there is also no opportunity to add semantic value here.

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?

Names a specific verb and resource ('Rebuild the cached library exclusion set') and immediately explains its relationship to the sibling recommendation tools, which all consume this set. An agent can distinguish this maintenance tool from recommend_* siblings without opening any schema.

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?

States the exact trigger ('Call this after adding songs to a playlist by other means') and explicitly contrasts it with the case where it is unnecessary, since liking a song is already picked up immediately. It also names the alternative workflow (a playlist-management tool) that creates the need.

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