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 states the tool returns 'Formatted tag information' but doesn't specify what that includes (e.g., description, usage stats, related tags), whether it's a read-only operation, potential rate limits, or error conditions. For a tool with zero annotation coverage, this leaves significant behavioral gaps unexplained.

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 and front-loaded with the core purpose in the first sentence. The Args/Returns sections are structured but could be more integrated. There's no wasted text, though it could be slightly more fluent by combining elements into a cohesive paragraph.

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 low complexity (2 parameters, no nested objects) and the presence of an output schema (which handles return values), the description is minimally adequate. However, with no annotations and 0% schema coverage, it lacks details on authentication needs, error handling, or example usage, leaving room for improvement in guiding the 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?

Schema description coverage is 0%, so the description must compensate. It adds minimal value: it names the parameters ('tag' and 'lang') and notes 'lang' is optional for wiki content, but doesn't explain what a 'tag' is (e.g., genre, mood), valid formats, or examples. For two parameters with no schema descriptions, this is insufficient to guide proper usage.

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 as 'Get information about a music tag' with a specific verb ('Get') and resource ('music tag'). It distinguishes itself from siblings like 'get_top_tags' (which lists popular tags) and 'get_tag_top_albums' (which gets albums for a tag) by focusing on detailed information about a specific tag. However, it doesn't explicitly contrast with all similar siblings like 'get_tag_weekly_charts'.

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 when to choose this over 'get_top_tags' (for listing tags) or 'get_tag_top_albums/artists/tracks' (for tag-specific rankings), nor does it specify prerequisites like authentication. The only implied usage is needing a tag name, but no explicit context or exclusions are provided.

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