Player rankings as of a date

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

Beyond the readOnly/openWorld/idempotent annotations, the description discloses the as-of lookup semantics (newest record on or before, never after), per-system data shape (ATP/WTA rank+points vs UTR rating), data availability start date for ITF/UTR, and plan requirement. No contradictions with annotations.

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?

Four sentences, each serving a distinct purpose: core definition, differentiation from current data, system-specific details, and coverage/access constraints. Front-loaded with the most important information.

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?

The tool is well-specified with a rich description covering historical semantics, system behavior, data coverage, and access requirements. The existing output schema covers return values, so the description's omissions are acceptable. There are minor unknowns like behavior before history begins, but the description explicitly notes the start date, so completeness is high.

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% for all three parameters, so baseline is 3. The description adds critical semantics beyond the schema: the 'newest record in force ON OR BEFORE as_of — never one dated after it' rule clarifies edge cases, and 'Systems are never collapsed' clarifies how the system parameter behaves. This goes beyond the basic baseline, though the schema already explains each parameter adequately.

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 a specific verb ('get') and resource ('player rankings'), and immediately scopes it to 'SPECIFIC players' and 'point-in-time' historical records. It explicitly contrasts with the API's other current-value ranking fields, distinguishing it from siblings like get_rankings.

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?

It establishes when to use this tool: when historical point-in-time rankings for specific players are needed, and explicitly notes that every other ranking field returns current values. It also adds a prerequisite (ULTRA plan). However, it does not name a specific alternative tool (e.g., get_rankings) or state exclusions like 'use get_rankings for current rankings'.

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