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

Beyond the readOnlyHint annotation, the description adds important behavioral details: omitted timeSpan returns all five time spans, and a null entry means the account is not ranked on that board due to no qualifying activity. This is valuable because there is no output schema to convey these semantics.

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 two tight sentences: the first front-loads the return payload and the optional parameter behavior, and the second clarifies null semantics. No filler or redundant restatement.

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 read-only tool with one optional parameter, no output schema, and no nested objects, this description covers everything an agent needs: return fields, single- vs all-time-span behavior, and null-entry meaning. The account-scoped nature also removes ambiguity against siblings.

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?

The input schema already fully documents the timeSpan enum and its description, so the description does not need to add much. It does add the useful note that omitting the parameter returns every time span, but the schema already carries the main parameter semantics.

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 verb and resource: it returns THIS account's PnL leaderboard rank, including rank, board size, PnL, ROI, and equity. It clearly distinguishes itself from a full-leaderboard tool by explicitly scoping to the current account, which separates it from sibling tools like get_leaderboard.

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 conveys when to use it: when the agent needs the current account's rank on the leaderboard, and optionally for a specific time span or all time spans by omitting timeSpan. It does not explicitly name alternatives or say when not to use it, but the 'THIS account' scoping provides clear contextual guidance.

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