Last.fm MCP Server

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It mentions the tool returns a 'formatted list' but doesn't specify format details, pagination behavior beyond the 'page' parameter, rate limits, authentication requirements, or error handling. For a read operation with no annotations, this leaves significant gaps in understanding how the tool behaves.

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 and appropriately sized. It starts with a clear purpose statement, followed by a bullet-point list of parameters and returns. Every sentence earns its place by providing essential information without redundancy. Minor improvements could include integrating the purpose more seamlessly, but it's highly efficient.

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 (4 parameters, no annotations, but with an output schema), the description is fairly complete. It covers all parameters in detail and notes the return type. The output schema likely handles return value specifics, so the description doesn't need to explain those. However, it lacks context on authentication or error cases, which could be important for usage.

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 description adds substantial meaning beyond the input schema, which has 0% description coverage. It explains each parameter's purpose: 'user' as the username, 'period' with specific time options, 'limit' with range and default, and 'page' with default. This fully compensates for the schema's lack of descriptions, making parameters clear and actionable.

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: 'Get a user's most played artists.' It specifies the verb ('Get') and resource ('user's most played artists'), making the function unambiguous. However, it doesn't explicitly differentiate from sibling tools like 'get_top_artists' (which might be global vs. user-specific), leaving room for minor ambiguity.

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 provides no guidance on when to use this tool versus alternatives. It doesn't mention sibling tools like 'get_user_top_tracks' or 'get_user_top_albums' for similar user-specific queries, or 'get_top_artists' for global top artists. Usage is implied by the tool name and parameters but not explicitly stated.

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