get_user_info

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description bears full responsibility for behavioral disclosure. It does not mention authentication requirements, error handling (e.g., user not found), response structure, or read-only nature. Only the defaulting behavior is noted.

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 a single, concise sentence that efficiently conveys the tool's purpose. It is front-loaded with the key information, though it could be slightly expanded to include more detail without becoming verbose.

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 simple tool with one parameter and no output schema, the description is adequate but not fully complete. It would benefit from indicating what fields are returned in the profile info or that the response is a JSON object.

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 100%, and the description adds meaningful context beyond the schema by explaining the default behavior using the MCP_LASTFM_USERNAME environment variable. This helps the agent understand optionality.

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 it retrieves a Last.fm user's profile info, using a specific verb-resource pair. It distinguishes from sibling tools like get_user_friends or get_user_loved_tracks by focusing on 'profile info', though it could be more precise about what that includes.

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 schema description provides guidance on when to omit the user parameter (defaults to env variable), which is useful. However, there is no explicit guidance on when to use this tool vs. other user-related tools, nor any exclusions or alternatives mentioned.

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