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

Annotations already cover read-only, idempotent, and non-destructive behavior, so the bar is lower. The description adds valuable context: the platforms covered and the credential requirements (e.g., private ESPN needs espn_s2 + swid), which the agent needs to know before calling. It doesn't contradict annotations and adds meaningful behavioral detail beyond them.

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, front-loaded with the primary use case ('Start here when NO profile is connected') and immediately routing to the alternative for connected users. Every sentence earns its place; no filler or redundancy.

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 simple list tool with no output schema, the description fully covers what the agent needs: what it returns (platforms, capabilities, sports, credentials), when to use it, and when to use the alternative. Combined with strong annotations (read-only, idempotent), nothing critical is missing for correct invocation.

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% for the single response_format parameter, with the enum values and default already documented. The description adds no additional parameter guidance beyond what the schema provides. With full schema coverage, 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 the specific purpose: list supported platforms (fantrax, espn, sleeper) with capabilities, sports, and credentials. It clearly distinguishes from siblings by framing itself as the starting point for unconnected users and explicitly names fantasy_get_my_setup as the alternative for connected users. This leaves no ambiguity about what the tool does.

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?

Explicitly states when to use it ('Start here when NO profile is connected') and when not to ('Connected users' leagues are already configured — see fantasy_get_my_setup instead'). It names the exact sibling to use instead, providing a clear routing decision for the agent.

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