Last.fm MCP Server

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It mentions that the tool returns a 'formatted list' but does not specify what 'most popular' means (e.g., based on plays, charts, user ratings), whether authentication is required, rate limits, error conditions, or pagination details beyond the page parameter. The description adds minimal behavioral context beyond the basic operation.

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 well-structured with a brief purpose statement followed by categorized parameter and return explanations. It is appropriately sized and front-loaded, though the 'Args' and 'Returns' sections could be integrated more seamlessly into prose.

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?

Given the tool's moderate complexity (5 parameters, no annotations, but with an output schema), the description is fairly complete. It covers all parameters and states the return type, though it lacks details on authentication, rate limits, and the definition of 'most popular.' The output schema existence reduces the need to explain return values in depth.

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?

The schema description coverage is 0%, so the description must compensate. It provides clear semantics for all 5 parameters: artist name, optional MBID for disambiguation, autocorrection behavior, result limit with range and default, and pagination with default. This adds significant value beyond the bare schema, though it could explain the autocorrect algorithm or MBID format more.

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 clearly states the tool's purpose with a specific verb ('Get') and resource ('artist's most popular tracks'), distinguishing it from sibling tools like get_artist_info, get_artist_top_albums, or get_top_tracks which serve different functions.

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 implies usage context through the parameter explanations (e.g., MBID for disambiguation, autocorrect for name variations), but does not explicitly state when to use this tool versus alternatives like get_artist_info or get_top_tracks. No exclusions or prerequisites are mentioned.

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