Get leagues for a user

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

With no annotations, the description carries the full behavioral burden. It discloses a two-step behavior (username resolution before listing), the default season behavior, and that the output contains league_id for reuse. It does not mention error cases, but the disclosed behavior is sufficient for a read-only lookup.

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?

Two sentences with no redundancy: the first states the operation and default, the second explains how to use the result. The key workflow constraint (league_id reuse) is front-loaded.

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?

For a two-parameter resolver with no output schema, the description provides the essential context: what the tool returns (a list of leagues with league_id) and how the result fits into the wider toolset. It omits error behavior, but that is a minor gap for this straightforward lookup.

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 username and season. The description restates the default season and refers to username resolution but adds no new parameter-level detail beyond the schema. Baseline 3 is appropriate.

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 states a specific action: resolve a Sleeper username to a user_id and list that user's NFL leagues for a season. It also clarifies the tool's role in the workflow by telling the agent to use the returned league_id with other tools, distinguishing it from the sibling tools that handle players, drafts, and rosters.

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 implies the tool is the entry point for user-league lookups: it resolves the username, lists leagues, and returns league_id for downstream tools. It does not explicitly name alternative tools or when not to use it, but the context is clear because the siblings serve different purposes.

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