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

Annotations already declare readOnly/idempotent/non-destructive/non-open-world, so the safety profile is covered; the description adds substantive behavioral boundaries beyond that — the jurisdictional and rent-control-area limits, the three specific legal tests applied, and an explicit statement of what it will not opine on. That is exactly the extra context a calling agent needs to trust and frame the result.

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 purpose, then scope, then outputs, then limits — a sensible order with no filler sentences. It is a single very long semicolon-chained sentence, which is dense but every clause carries distinct information.

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 five-parameter read-only checker with an output schema and full annotations, the description supplies everything still needed: scope, the decision rules, the two derived outputs (new rent start date, referral deadline), and the fairness disclaimer. Nothing an agent requires to call it correctly is missing.

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 schema already documents all five inputs and their enums. The description nevertheless adds meaning by tying parameters to the legal rules they feed (three months' notice from `received` to `starts`, the 12-month lookback on `history`/`lastIncrease`, the `prescribedForm` test), which helps an agent supply correct values.

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 (check), a specific resource (a landlord's rent-increase notice), and narrows scope to private residential tenancies in Scotland outside rent control areas. It then enumerates the exact questions answered, so an agent can tell it apart from check_rent_increase_notice and the other check_* siblings without opening a 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?

Gives clear applicability conditions ('private residential tenancy in Scotland, outside a rent control area') and an explicit exclusion ('it does not judge whether the new rent is fair'), which is real when-to-use guidance. What it lacks is naming an alternative tool for notices outside that scope, which would be needed for a 5.

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