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

Annotations already declare a safe read, but the description adds cost (5 credits), the legal caveat that UPRN linkage does not verify the demise (garage/parking/sibling titles), the 'status: no_lease' interpretation limit, and the warning that the AVM does not adjust for a short term. These are behavioral constraints an agent cannot infer from structured fields.

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 what the tool returns, followed by caveats, then the calling workflow last. Every sentence is load-bearing, though the dense run-on enumeration and stacked disclaimers make it heavier than necessary for a one-parameter tool.

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?

An output schema exists, so return-value detail is not required; the description instead supplies the missing operational context: cost, geography, UPRN keying, upstream chaining, truncation disclosure expectations, and the critical caveat that no_lease does not prove freehold tenure.

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 parameter has 0% schema description coverage, so the description carries the burden and does compensate: it specifies the parameter is a UPRN identifier (not an address string) and that it must be obtained via address_autocomplete/address_resolve. It stops short of stating expected format or invalid-UPRN behavior.

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 ('Registered leases linked to this UPRN') and enumerates the payload: longest-expiry record plus up to ten alternatives, register property descriptions, title/record identifiers, and computed remaining term. This distinguishes it clearly from ownership_by_title, property_lease_batch, and property_lookup without opening their schemas.

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 routes keying ('Keyed on a UPRN, not an address: call address_autocomplete (free) to narrow, then address_resolve to get one') and scopes geography and cost ('UK only. Costs 5 credits (5p)'). It does not state when to prefer property_lease_batch or property_report over this single-UPRN call, so it falls short of full when/when-not guidance.

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