io.github.simonmak-ascent/fair-value

Black-Scholes option price

black_scholes_price

Read-onlyIdempotent

Price a single European call or put with the Black-Scholes-Merton model. Input spot, strike, maturity, risk-free rate, and volatility to return the option price and used inputs.

Instructions

Price a European call or put with the Black-Scholes-Merton model. Use this for a single European option; for swaps, convertible bonds, futures, or greeks use the delegated derivatives tools. Returns the option price and the inputs used.

Input Schema

TableJSON Schema

Name	Required	Description
`spot`	Yes	Current underlying spot price.
`strike`	Yes	Option strike price.
`maturity`	Yes	Time to expiry in years (e.g. 0.5 for six months).
`risk_free`	Yes	Continuously-compounded risk-free rate as a decimal.
`volatility`	Yes	Annualized volatility of the underlying as a decimal.
`option_type`	No	Option type; defaults to 'call' when omitted.

Output Schema

TableJSON Schema

Name	Required	Description
`error`	No	Error detail, present only when status='error'.
`steps`	No	Ordered computation steps, when the method reports them.
`value`	No	Primary result: a number for scalar tools, an object for valuation tools.
`method`	No	Method or tool name that produced the result.
`status`	Yes	'ok' on success, 'error' on failure.
`ticker`	No	Ticker the result pertains to, when applicable.
`assumptions`	No	Inputs and assumptions used, echoed for traceability.
`formula_ref`	No	Formula or standards reference for the method.
`data_timestamp`	No	ISO-8601 UTC timestamp of the underlying data, when fetched.

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 3, 2026

TDQS

A4/5.0

Behavior3/5

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

Annotations already establish this is a read-only, idempotent, non-destructive computation, so the description's main added value is the soft hint that it is a pure pricing function. It notes the return contents, but an output schema already exists, so the description adds little behavioral context beyond the structured data.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences, zero padding, and the core capability is front-loaded ahead of the alternative-tool routing.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With a 100%-documented schema and an output schema present, the description covers what an agent needs to select and call the tool. It could note key model assumptions (e.g. no dividend yield, European exercise only beyond the single mention) but is otherwise adequate.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and each input (spot, strike, maturity, risk_free, volatility, option_type) is fully described in the schema. The description adds only the model-level constraint that inputs must correspond to a European option; it contributes no unit or format detail beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (price), resource (European call/put), and named model (Black-Scholes-Merton). It also draws a boundary against swap, convertible bond, futures, and greeks tools, so an agent can route correctly without inspecting siblings.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly scopes usage to a single European option and lists what to use instead for swaps, convertible bonds, futures, and greeks. The alternatives are referred to generically as 'the delegated derivatives tools' rather than by concrete tool name, which leaves a small routing gap.

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