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

Annotations cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description's burden is lower. It adds real behavioral context by emphasizing the tool is pure arithmetic and not connected to live market data, which no annotation conveys. It doesn't mention output shape, but that's minor for a calculator.

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 sentences, front-loaded with the core action and followed by the scope-restricting disclaimer. Tight and waste-free, though the 'not a...' list is slightly listy and could be trimmed.

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 no output schema and 0% param coverage across 5 params, the description leaves gaps an agent would want filled: return structure (per-scenario P&L?), role of entryCostUsd/exitCostUsd, and the 12-item array limit. The arithmetic-only framing is a strong addition, but overall it is adequate rather than complete.

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 0% and there are 5 parameters, so the description must compensate. It does communicate the semantic of contracts+entryPrice+scenarioPrices as 'fixed number of contracts' and 'user-selected outcome prices', and mentions entry/exit dollar costs. But it never explains bounds (prices 0-1), the up-to-12 scenarioPrices array, or units/precision, leaving meaningful ambiguity.

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+resource: calculate the dollar impact of user-selected outcome prices over a fixed contract count with explicit entry/exit costs. It also sharply delimits itself from siblings (none of which compute anything) via the 'pure arithmetic: not a forecast, live quote, strategy backtest, order or paper position' clause.

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 negative framing ('not a forecast, live quote, strategy backtest, order or paper position') implicitly tells the agent when NOT to use it, which is genuinely useful given siblings like inspect_prediction_market. But it never states when TO use it or names an alternative for the scenarios it excludes.

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