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

Annotations already cover readOnly/idempotent/non-destructive, and the description goes well beyond them: data coverage boundaries (opening/closing only from June 2020), expected book depth (median 5-7, sometimes one since mid-2024), per-call credit costs, and an explicit policy prohibition on staking, payout math, bet recommendations or sportsbook referrals.

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 dense sentences, front-loaded with what the tool returns before coverage caveats, cost, and the safety constraint. No sentence is filler; the credit costs and data-limits sentence both carry decision-relevant 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?

An output schema exists, so return shape needn't be spelled out, yet the description still names the key fields. Coverage windows, book depth, cost, and the no-betting-advice guardrail leave nothing an agent needs in order to call this correctly.

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 the baseline is 3, but the description adds real meaning: it frames bout_id and event_id as mutually exclusive access scopes and attaches distinct credit costs to each. League's enum behavior is left entirely to 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?

States a specific verb and resource: betting lines with opening, closing and current moneyline for both fighters, plus implied probabilities and the total-rounds line. The scope ('each posted sportsbook's') cleanly separates it from get_line_movement and get_fight, which an agent can distinguish without opening a 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 routes between the two access modes: bout_id for one fight (5 credits) or event_id for a whole card (10 credits), and states when data is unavailable (pre-June 2020). It does not name get_line_movement as the alternative for movement-over-time questions, which is the one routing gap.

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