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 full burden. It mentions the tool returns a 'formatted list' but lacks details on behavioral traits such as rate limits, authentication requirements, error handling, or pagination behavior beyond parameter hints. The description does not contradict 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 well-structured and front-loaded with a clear purpose statement, followed by organized parameter and return sections. Every sentence adds value without redundancy, making it efficient and easy to parse.

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 has output schema), the description is fairly complete. It covers purpose and parameters adequately, and the output schema handles return values, though it lacks context on authentication, errors, or rate limits which would be helpful for a user-focused tool.

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 0%, so the description must compensate. It adds meaningful semantics for all parameters: clarifies 'user' as a username, lists valid 'period' values with defaults, specifies 'limit' range and default, and explains 'page' for pagination. This goes beyond the bare schema, though some details like exact formatting are still missing.

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 ('user's most played tracks'), distinguishing it from sibling tools like get_user_recent_tracks or get_top_tracks by focusing on personal top tracks based on play 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 implies usage for retrieving a user's top tracks but does not explicitly state when to use this tool versus alternatives like get_user_top_artists or get_user_top_albums. No guidance on prerequisites (e.g., authentication) or exclusions is provided.

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