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. It discloses that authentication is required, which is a critical behavioral trait. However, it doesn't mention potential side effects (e.g., permanent removal from loved list), rate limits, or error conditions, leaving some behavioral aspects unspecified.

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 front-loaded with the core purpose, followed by authentication requirements, then parameter and return details in a structured format. 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 complexity (mutation with authentication), no annotations, and an output schema (which covers return values), the description is mostly complete. It covers purpose, prerequisites, and parameters, but lacks details on error handling or behavioral nuances, which could be beneficial for an agent.

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 lists both parameters ('artist' and 'track') and explains their purpose ('Artist name', 'Track name'), adding essential meaning beyond the bare schema. However, it doesn't provide format details (e.g., case sensitivity) or examples.

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 action ('Remove love from a track') and the resource ('on your Last.fm profile'), distinguishing it from sibling tools like 'love_track' (which adds love) and 'get_user_loved_tracks' (which reads loved tracks). It specifies the exact operation without 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 explicitly states when to use this tool: 'Requires authentication - use authenticate_user() and get_session() first.' This provides clear prerequisites and distinguishes it from tools that don't require authentication, such as 'get_track_info' or search tools.

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