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. It mentions 'Formatted list of matching albums with their stats' in the Returns section, which adds some behavioral context about output format. However, it lacks critical details: whether this is a read-only operation, rate limits, authentication requirements, error handling, or pagination behavior beyond the 'page' parameter. For a search tool with no annotations, this is insufficient.

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 the core purpose. It uses sections (Args, Returns) efficiently, with no redundant sentences. Every part earns its place by clarifying parameters and output, 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 (search with pagination), no annotations, and an output schema (implied by 'Has output schema: true'), the description is minimally adequate. It covers parameters and output format but lacks behavioral context (e.g., safety, limits) and usage guidance. The output schema reduces the need to detail return values, but gaps in other areas keep it from being complete.

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 provides clear semantics for all three parameters: 'query' as 'Album name or search query', 'limit' with range and default, and 'page' with default. This adds meaningful context beyond the bare schema (which only has titles and types). However, it doesn't explain parameter interactions or validation rules, preventing a perfect score.

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 albums on Last.fm by name'. It specifies the verb ('Search'), resource ('albums on Last.fm'), and scope ('by name'). However, it doesn't explicitly differentiate from sibling tools like 'search_artists' or 'search_tracks' 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_album_info' (for detailed info on a known album) or 'search_artists/tracks', nor does it specify prerequisites (e.g., authentication needs) or contextual constraints. Usage is implied only by 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.