x-mcp

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 the return fields ('bio, metrics, verification status, etc.') but lacks critical behavioral details: authentication requirements, rate limits, error handling (e.g., for invalid inputs), or whether it's read-only (implied but not stated). For a lookup tool with zero annotation coverage, this is inadequate.

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: two concise sentences that directly state the action and returns. Every sentence earns its place with no wasted words.

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 complexity (a lookup tool with 2 parameters) and lack of annotations/output schema, the description is incomplete. It omits authentication needs, error cases, and detailed return structure (beyond a vague list). For a tool in a social media context with siblings like delete_tweet, more context on safety and usage is warranted.

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%, so the schema already documents both parameters (username and user_id). The description adds minimal value by restating 'by username or user ID' without clarifying exclusivity, precedence, or format beyond the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

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: 'Look up a user profile by username or user ID' (specific verb+resource). It distinguishes from siblings like get_followers or get_timeline by focusing on user profiles rather than social interactions or content. However, it doesn't explicitly differentiate from get_metrics (which might overlap with 'metrics' in returns).

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., authentication), exclusions, or comparisons to siblings like get_metrics (which might handle similar data). The context is implied but not explicit.

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