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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered by structured data. The description's added detail is about computed outputs rather than behavior — it says nothing about determinism versus live lender rates, error conditions, or rounding conventions beyond what the annotations imply.

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?

A single front-loaded sentence with the verb first and the deliverables after. It is dense but every listed output earns its place, especially since there is no output schema; a slightly clearer grouping of inputs versus outputs would improve it marginally.

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 usefully enumerates the returned figures, which is the most important gap to close for a calculator. It omits what the required-vs-defaulted parameter split means in practice and gives no sense of result precision or which figures are null when monthlyRent is left at 0.

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%, with units, defaults, ranges and an enum already documented per parameter, so the schema does the heavy lifting. The description connects a few concepts to parameters implicitly (ICR to monthlyRent, stress tests to interestRate) but adds no format, unit, or interaction detail beyond the schema.

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 opens with a specific verb and resource ('Calculates a UK buy-to-let mortgage') and enumerates exactly which figures are produced (loan amount, LTV, payments, total interest, ICR, stress tests). This implicitly separates it from siblings like analyse_buy_to_let_deal or check_deal, though it never names or contrasts with an alternative.

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?

There is no when-to-use, when-not-to-use, or prerequisite guidance. An agent cannot tell from the text whether this should precede analyse_buy_to_let_deal, feed into it, or be used standalone, nor that only propertyValue is required and everything else defaults.

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