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

Annotations already declare this read-only, idempotent and non-destructive, so the safety profile is covered. The description adds genuine domain context beyond them: which deposit type is capped in each nation (England both, Wales holding only, Scotland and NI tenancy only), which tells the agent what the result will and will not contain. Return shape is covered by the output schema.

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 that front-loads the core computation and appends the optional check, followed by the jurisdiction caveat. No filler, and the most important information (what it computes) comes first.

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 read-only, idempotent calculation tool with a full output schema and 100%-documented parameters, this covers scope, jurisdiction coverage and the optional validation path. Slightly more could be said about how non-monthly rent periods (week/four_weeks) are normalised, but the essentials are present.

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 the baseline is 3; the description earns an extra point by clarifying that depositAsked is an optional validation input ('optionally check a deposit the user was asked for') and that the core computation is driven from the rent figure, framing the required-vs-optional distinction in one clause.

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 precise verb+resource: works out the maximum tenancy and holding deposit from rent, for any UK nation, with an optional check of a deposit already asked for. This is clearly distinguishable from siblings like check_rent_increase_notice or check_notice_period, which cover different regulatory questions.

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 makes the trigger condition clear: computing statutory deposit caps from a rent figure, and optionally validating an amount the user was quoted. It gives clear context but does not explicitly route the agent away from or toward any named sibling, so it stops short of the 5 bar.

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