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

Annotations cover the safety profile (readOnly, non-destructive, closed-world), and the description adds substantial domain behavior on top: coin settlement means P&L and caps come back in BTC/ETH not USD, the scenarioPnlUsd conversion exists, a long call's upside is capped while a long put's is unbounded, and null caps mean unbounded. It even pre-empts the natural 'this looks like a bug' reaction to the asymmetric payoff shape.

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 output list, then the coin-settlement explanation. It is dense and longer than most definitions, but nearly every sentence carries non-obvious information (settlement denomination, capped vs unbounded upside). Slightly over-explained in the payoff-shape passage, costing a point.

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, the description enumerates the return fields (intrinsicPerUnitCoin, scenarioPnlCoin, scenarioPnlUsd, breakevenPrice, maxLossCoin/maxProfitCoin, isProfitable) and explains the null-means-unbounded convention. Combined with the settlement context, an agent has everything needed to call and interpret the tool.

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 interpretive meaning the schema lacks: it explains that premiumCoin is coin-denominated per unit (matching Deribit quotes) and that coin settlement is why P&L is reported in the base coin. This clarifies the units and semantics of the numeric inputs rather than just restating them.

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+scope: 'Payoff, P&L, and breakeven price for a single-leg Deribit BTC/ETH option (long or short call/put) at a given scenario price at expiry.' The 'single-leg' qualifier implicitly separates it from multi-leg siblings like run_spread_payoff or run_straddle_strangle, 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?

Gives two concrete trigger phrases ('what does my BTC call/put pay off at price X?', 'where's my breakeven on this option?'), which is clear context for when to use it. It does not explicitly name the alternative to reach for a multi-leg payoff (e.g. run_spread_payoff), so the exclusion is only implied by 'single-leg'.

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