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 the return format ('Formatted list of matching tracks with their stats'), which adds some value, but fails to cover critical aspects like rate limits, authentication requirements (implied by sibling tools like 'authenticate_user'), pagination behavior beyond the 'page' parameter, or error handling. This is a significant gap for a search tool in an API context.

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 efficiently structured: a clear purpose statement followed by bullet-point-style sections for 'Args' and 'Returns'. Every sentence adds value without redundancy, such as specifying defaults and ranges directly. It's front-loaded with the core functionality, making it easy to scan and understand quickly.

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 partially complete. It covers parameter semantics well and mentions the return format, but lacks behavioral details like authentication, rate limits, or error handling. The output schema likely handles return values, so that gap is acceptable, but overall it's adequate with clear room for improvement in usage and transparency.

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 meaningful context beyond the input schema, which has 0% description coverage. It explains that 'query' is for 'Track name or search query', 'artist' is 'Optional artist name to narrow search', and provides ranges and defaults for 'limit' (1-50, default: 10) and 'page' (default: 1). This compensates well for the schema's lack of descriptions, though it doesn't detail the 'stats' in returns or advanced query syntax.

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: 'Search for tracks on Last.fm by name.' It specifies the verb ('search'), resource ('tracks'), and platform ('Last.fm'), making the action clear. However, it doesn't explicitly differentiate from sibling tools like 'search_albums' or 'search_artists' beyond the resource type, which prevents a perfect score.

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_track_info' for detailed info on a known track or 'get_similar_tracks' for recommendations, nor does it specify use cases like finding tracks by partial names versus exact matches. This lack of context leaves the agent to infer usage.

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