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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so "All tools are read-only" is largely a restatement of structured data. The genuinely additive behavior info is that the tool is a bootstrap/discovery call whose usefulness depends on whether a profile exists.

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 compact sentences with the payload contents front-loaded and the usage condition second. The embedded user-question parenthetical is mildly redundant but useful for retrieval matching, so the text is efficiently sized overall.

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?

There is no output schema, but the description enumerates the returned fields (platforms, capabilities, sports, credentials), which is exactly what an agent needs for a zero-required-param discovery tool. An agent has enough to call and interpret it without further detail.

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?

Only one parameter (response_format) and schema coverage is 100%, so the schema already documents the markdown/json choice and its default. The description adds no additional parameter guidance, which meets the baseline for fully documented params.

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?

States a specific verb+resource (list fantasy providers) and enumerates what each entry contains: platforms (fantrax, espn, sleeper), capabilities, sports, and credential requirements. This clearly separates it from league-scoped siblings like fantasy_list_user_leagues, though it never names a sibling explicitly.

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?

"Start here when NO profile is connected; a connected profile's leagues are already configured" gives a concrete entry condition and implicitly excludes the case where a profile already exists. It stops short of naming the alternative tool to use when a profile IS connected.

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