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

Annotations already cover readOnly/idempotent/non-destructive, and the description adds substantial context beyond them: per-item outcome codes (ok | no_lease | not_found | error) in input order, per-property charging capped at the sum of single calls, the 5-credit price, and a UK-only constraint. That is rich behavioral disclosure.

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?

Two tight sentences, front-loaded with the core action and pricing, with no filler. Every clause earns its place.

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 an output schema present handling return values, the description covers scope, pricing, outcome codes, geographies, and the UPRN prerequisite chain — everything an agent needs to call it correctly.

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?

The single required parameter is uPRNs, and though schema coverage is 0%, the description clarifies the keying ('Keyed on a UPRN, not an address') and the 100-item ceiling, adding meaningful semantics beyond the bare name.

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 states a specific verb+resource ('`property_lease` for up to 100 properties in one call') and its batch semantics, making clear it is the bulk form of the `property_lease` sibling. An agent can distinguish it from the single-property tool without opening either 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?

It gives clear when-to-use context ('up to 100 in one call') plus a prerequisite workflow: 'call `address_autocomplete` (free) to narrow, then `address_resolve` to get one.' Explicit exclusions are thin, but the operational context is well-defined.

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