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 for behavioral disclosure. While 'Get' implies a read operation, it doesn't specify whether this requires authentication, rate limits, error conditions, or what 'formatted' output entails. For a user data tool with zero annotation coverage, this leaves significant behavioral gaps about permissions, privacy, and response structure.

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 appropriately sized with three brief sections (purpose, args, returns). Each sentence earns its place by covering essential aspects. However, the structure could be more front-loaded by integrating the parameter explanation into the main description rather than a separate 'Args' block.

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 one parameter, no annotations, but an output schema exists, the description is moderately complete. The output schema will document return values, so the description needn't detail them. However, for a user data tool, it lacks context about authentication needs, data sensitivity, or error handling, which are important for safe invocation.

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 minimal value: the Args section clarifies 'user' is a 'Username to get info for', but doesn't specify format constraints (e.g., case sensitivity, special characters) or provide examples. With only one parameter, the baseline is 4, but the description's limited semantic detail reduces this to 3.

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 user profile information' - a specific verb ('Get') and resource ('user profile information'). It distinguishes from siblings like 'get_user_loved_tracks' or 'get_user_top_artists' by focusing on general profile data rather than specific user activity metrics. However, it doesn't explicitly contrast with authentication-related tools like 'authenticate_user' or 'get_session'.

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 prerequisites (e.g., whether authentication is required), nor does it differentiate from sibling tools that also retrieve user-related data like 'get_user_recent_tracks' or 'get_user_top_albums'. The agent must infer usage context solely from the tool name and description.

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