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

Annotations cover read-only/idempotent/non-destructive, and the description adds genuinely non-obvious behavior: computations use the higher of price and reference value, women-buyer rates apply, a 1% Mumbai metro surcharge exists, and unsupported states return 'not computed' rather than an error or estimate. That last point is important output behavior and is not derivable from any structured field.

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?

Front-loaded with the jurisdiction tag and the core action, then coverage, computation basis, and the no-figure fallback — every clause carries information. The single dense sentence is slightly heavy but not padded.

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 carries return-value burden and does so partially, telling the agent that uncovered states yield 'not computed' with no figure. It leaves the shape of a successful result (duty amount, registration fee, breakdown) implicit, which is the main remaining gap for a 6-parameter calculation tool.

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 coverage is 100%, so baseline is 3, but the description adds real meaning: reference_value is consumed via a max() against price (not a simple override), and mumbai/woman_buyer are tied to specific rate adjustments. This explains how parameters interact rather than merely restating their names.

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+resource (computes stamp duty and registration fee on a home purchase) scoped precisely to India and named states/UTs. It distinguishes itself from the many sibling tax tools (purchase_duty_au, purchase_tax_uk, transfer_tax_us, frais_notaire_fr) by jurisdiction and by naming exactly which states it covers. An agent can identify the tool and its coverage without opening the schema.

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?

Explicitly states the positive case (seven covered states) and the negative case (Delhi, Karnataka, Tamil Nadu return 'not computed' with no figure), so the agent knows when not to rely on it. It doesn't name an alternative tool for uncovered states, but that exclusion is clear enough to route correctly.

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