sleeper_user

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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, so the safety profile is covered. The description adds valuable behavioral context beyond annotations: it specifies the exact return fields ({user_id, username, display_name, avatar, is_bot}), states that no auth is needed, and clarifies the distinction between username and user_id input. It doesn't mention error cases or rate limits, but for a simple lookup tool this is adequate.

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 compact and well-structured: purpose, return values, example, and auth in four short lines. Every sentence earns its place, and the example is directly useful. No fluff or redundant details.

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 simplicity (1 parameter, no output schema), the description provides everything needed: input format, return fields, and downstream usage. It even tells the agent what to do with the result. Annotations cover the safety dimensions, so no additional behavioral details are necessary for effective use.

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 coverage is 100% and the schema description already explains that username_or_id is 'Sleeper username, or a numeric user_id... part of the URL path'. The description's example and mention of 'username (or user id)' add little beyond the schema. It does reinforce the dual nature of the parameter, but baseline 3 is appropriate since the schema carries 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 action: 'Look up a Sleeper user by username (or user id)'. It also positions it as 'the first step to finding someone's leagues', which differentiates it from sibling tools like sleeper_user_leagues and sleeper_league. This is a specific verb+resource with a defined scope.

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 explicitly guides when to use this tool: it's the first step to finding leagues, and it states that the returned user_id is what 'sleeper_user_leagues needs'. This provides clear contextual guidance and a next step, effectively telling the agent when and how to chain this tool with others.

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