rediscovery_candidates

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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, so the safety profile is covered. The description adds value by disclosing that it uses an explainable heuristic rather than a Last.fm recommendation endpoint, which clarifies the data source and method. It does not fully explain the heuristic, but that is not required; the note about explainability is a meaningful addition beyond annotations.

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 description is two concise sentences, front-loaded with the core purpose and a distinguishing note. Every word contributes to understanding the tool's function and its relationship to Last.fm's native recommendation system. No fluff or repetition.

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 tool has 5 parameters and no output schema, so the description must carry more weight. It explains the purpose and the heuristic nature, but omits any information about return values, pagination, or how the parameters influence results. An agent would not know what output to expect or how to tune the tool, making this incomplete for a parameter-rich tool without an output schema.

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 only 40% (username and historicalPool have descriptions, but limit, recentPeriod, and minHistoricalPlays do not). The tool description itself does not mention any parameters or provide any additional meaning. With low schema coverage, the description carries the burden to explain parameters, and it fails entirely, leaving the agent without guidance on how to set values or interpret their effects.

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 uses a specific verb ('Find') and resource ('historically significant artists with little or no listening in a recent Last.fm period'). It explicitly distinguishes itself from a recommendation endpoint, which sets it apart from typical recommendation tools. Among siblings (top_items, recent_scrobbles, artist_history), this is clearly about rediscovery candidates, not current top items, recent plays, or a single artist's history.

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 clearly implies when to use this tool: when you want to surface under-heard historical artists. It also states what it is not (a recommendation endpoint). However, it does not explicitly name alternative tools or give 'use X instead when Y' guidance. The context is clear but exclusions are only implied, not stated.

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