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

With no annotations, the description carries the full burden and does reasonably well: it declares the computation is deterministic closed-form math (i.e., pure, no side effects) and discloses a real operational requirement most tools omit — x402 payment of $0.01/call in USDC on eip155:8453. It does not disclose failure behavior for degenerate inputs (zero vol, zero time to expiry) or whether results are cached.

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?

The description is front-loaded with capability and return values, and the pricing detail is placed last so it does not obstruct the core purpose. It is slightly padded by the promotional clause "the numbers agents should quote instead of hallucinating option values," which restates what deterministic math already implies.

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?

There is no output schema, so the description must define the return shape, and it does list price plus five Greeks. However, for Greeks the units and conventions are the crux — theta per year vs per day, vega per 1% vol move, rho per 1% rate — and none of that is specified, leaving an agent unable to interpret the output 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 description coverage is 100%, so the seven parameters are already documented and the baseline is 3. The description adds only marginal semantic value: it confirms dividend yield is supported (validating divYieldPct) and that both call and put are accepted, but it never clarifies units or scaling — e.g., that volPct/ratePct are entered as whole percentages (5, not 0.05) or how years should be fractionalized.

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 a specific verb and resource — European option pricing via Black-Scholes-Merton — and enumerates exactly what is returned (price plus delta, gamma, theta, vega, rho) with dividend yield support. No sibling in the list does option pricing, so the risk of confusion with finance_roi_calculator or finance_cagr_calculator is minimal and the scope is unambiguous.

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 gives an explicit trigger: "Use this when an agent needs to black-Scholes price + all five Greeks," and adds the framing that this is the deterministic source of truth for option values. It does not state exclusions — e.g., that it covers European exercise only and not American/Binomial pricing or implied volatility — so an agent could wrongly reach for it on those cases.

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