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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety and external-data posture are covered. The description adds the data source (Baseball Savant) and directs the agent to mlb_discovery for valid values, but says nothing about pagination behavior, defaults, or size limits beyond what the schema documents.

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 tight sentences: capability first, then disambiguation and cross-references. No filler, no repetition of schema content, and the core action is front-loaded.

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 an output schema present, return values need no explanation, and all 15 parameters are documented in the schema. The description covers purpose, entity scope, and sibling routing; only richer behavioral notes (paging, limits) are absent, which is a minor gap for a read-only fetch.

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% with 15 well-annotated parameters, so the schema already carries the parameter semantics. The description adds no format or constraint detail beyond what the schema states, making the baseline 3 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?

States a specific verb (Fetch) plus the exact resource (Baseball Savant Fielding Run Value rows) and the entity scope (fielders, teams, batters, pitchers). It also distinguishes itself from sibling metrics tools by name, so an agent can route without opening the schema.

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 names alternatives for related metrics (mlb_statcast_run_value, mlb_statcast_oaa) and points to mlb_discovery for accepted values, which is genuine routing guidance. It stops short of stating the condition that should select this tool over those alternatives, so it is clear context but not full when/when-not guidance.

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