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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower; the description still adds real behavioral context by listing returned metrics and the sample-size floors that make each window meaningful. It omits default behavior when optional filters are omitted, which is the one remaining behavioral gap.

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?

Three dense sentences, front-loaded with the core purpose, then window semantics, then return payload — no filler. The metric list is long but each item is informative, so it stays close to optimal.

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?

With 7 optional parameters and no output schema, the description does the right work by enumerating return metrics and window thresholds. It falls short of complete because all parameters are optional and the description never states defaults for split, window, or sort, leaving the agent to guess the no-argument behavior.

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%, so baseline is 3, but the description goes beyond the enums by attaching a concrete meaning to 'season' (40+ PA) and 'l30' (20+ PA), which affects how an agent should interpret and trust the output. It does not explain sort_by/sort_dir or limit semantics beyond the schema.

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 first sentence states a specific resource and verb-like scope: hitter performance against LHP/RHP, i.e. platoon splits for batters. That implicitly distinguishes it from invoke_mlb_pitcher_splits and invoke_mlb_team_splits, but neither sibling is named, so differentiation requires inference.

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 explains the two window options and their minimum PA thresholds, which is parameter help rather than usage guidance. It never says when to reach for this instead of invoke_mlb_pitcher_splits, invoke_mlb_matchup, or invoke_mlb_probable-style teammates, and gives no exclusions.

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