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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds real value beyond that: a Pro entitlement requirement and the behavior that the answer explicitly reports when the account lacks Pro. It does not describe output shape or any latency/limits, but with no output schema that is a minor 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 tight sentences: trigger conditions first, then the return scope, then the entitlement constraint. Every clause earns its place and nothing is buried.

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 4-parameter read tool with no output schema, the description covers purpose, triggering questions, season scope, and the Pro gate. The remaining gap is what the returned splits actually look like (e.g., on/off ratings vs. share percentages), which the description only gestures at.

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 each parameter (including teammate_id's 'two-man / with-without splits' and season default) is already documented. The description adds only indirect meaning by specifying what split types exist per league; it gives no extra guidance on when to supply teammate_id versus omit it.

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 names the specific resource and scope: on/off splits, clutch/garbage-time splits, and with/without teammate splits, plus an NFL-specific variant (target/carry/red-zone shares). It is clearly distinguishable from siblings like player_profile or head_to_head, though the framing is usage-first rather than a crisp verb+resource statement.

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 opens with an explicit 'Use this when the user asks...' trigger list covering the three main question shapes, which is strong when-to-use guidance. It does not name a when-not condition or a specific alternative sibling (e.g., use player_profile for overall stats), so it stops short of a 5.

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