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

Beyond the readOnly/idempotent annotations, it discloses credit cost (5), the aggregation rule ('only identical lines are combined'), how many books back each number, and the timing semantics of the default snapshot (latest until kickoff, closing after). These are meaningful operational traits the annotations do not cover.

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?

Front-loaded with the core purpose and scope contrast, followed by aggregation rule, defaults, alternative tool, cost and usage constraint. Every sentence carries information; nothing is repeated from the schema or annotations.

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 simple (2 params, output schema present) and the description covers scope, defaults, cost, aggregation semantics and the sibling to use for raw prices. Nothing needed to invoke it correctly is missing.

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 both parameters are already documented and the baseline applies. The description's note on snapshot timing adds only a small nuance beyond the schema's 'last pre-game price so far' and says nothing further about game_id format.

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 (average implied vs. fair probability for moneyline, spreads and totals for one game) and immediately contrasts scope with per-book pricing. It is clearly separable from get_odds, get_market_odds and get_prop_probabilities.

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 the condition for use ('what the market thinks of one game, not any one book's price') and routes the alternative case to get_odds. It also gives the default-vs-request rule for opening lines, so the agent knows when to pass snapshot_type=opening.

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