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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely useful behavioral context beyond that: the rates are current and sourced from HMRC, Revenue Scotland and the Welsh Revenue Authority, and the calculation includes the HM Land Registry fee.

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 dense sentence, front-loaded with the jurisdiction and the action verb, followed by scope, situations and provenance. Every clause carries information; there is no padding.

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?

For a four-parameter, read-only calculator with no output schema, the description covers jurisdiction, regime selection, buyer situations, surcharges and rate provenance. It does not indicate what the result contains (e.g. a tax breakdown vs a single figure), which is the only remaining gap.

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 every parameter (price, nation, situation enum, non_resident) is already documented with meaning and constraints in the schema. The description restates the situation and residency dimensions but adds no syntax or format detail beyond what the schema supplies, so the baseline 3 applies.

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 and resource ('Computes the tax on buying a home') and enumerates the exact regimes covered (SDLT for England/NI, LBTT for Scotland, LTT for Wales). An agent can distinguish this from sibling tools like stamp_duty_in, purchase_duty_au and transfer_tax_us purely from the description.

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 clear context for when the tool applies, including the three buyer situations (mover, first-time buyer, additional property) and the non-UK resident surcharge. It stops short of naming alternatives or exclusions (e.g. when to prefer guide_uk or compare_nations_uk), so it is clear but not fully routing-aware.

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