UK Stamp Duty Calculator (SDLT / LBTT / LTT)

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

Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true. The description adds valuable behavioral details: it handles specific surcharges, first-time buyer relief, non-resident surcharge, corporate flat rate, and commercial property. It also mentions using 'current 2026 bands' and the source (Fox Davidson, FCA-authorised). No contradiction with annotations.

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 comprehensive but slightly verbose (multiple sentences). It front-loads the core purpose and follows with specific use cases and return format. Every sentence earns its place, but could be trimmed slightly without losing clarity.

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?

The tool has no output schema, but the description explicitly states what is returned: 'Returns banded breakdown, total tax payable and effective rate.' Combined with thorough coverage of regions, buyer types, surcharges, and reliefs, the description is complete for the tool's complexity (3 parameters, simple output).

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% for all three parameters. The description goes beyond the schema by explaining the effect of each buyer_type enum value (e.g., 'ftb' triggers FTB relief in England/NI up to GBP 500k, Scotland up to GBP 175k, none in Wales; 'nonresident' adds 2% surcharge only in England/NI). This adds significant meaning beyond the enum labels.

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 starts with a clear verb-resource pair: 'Calculate UK stamp duty on a property purchase across England/Northern Ireland (SDLT), Scotland (LBTT) and Wales (LTT).' It explicitly lists all supported tax types and regions, and distinguishes from the only sibling tool (a mortgage qualification tool) by focusing on stamp duty calculation.

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?

The description ends with an explicit usage statement: 'Use when a user asks about stamp duty, SDLT, LBTT, LTT, additional dwelling surcharge, ADS, first-time buyer relief, non-resident surcharge, or tax on a specific UK property purchase.' This covers when to invoke the tool and implicitly tells the agent not to use it for mortgage qualification queries.

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