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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world). Beyond that, the description adds two genuinely new behavioral facts: a credit cost of 15 and the England & Wales geographic restriction, both of which affect invocation decisions.

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?

Three short fragments, front-loaded with the core purpose, then scope, then cost. Nothing is wasted and there is no filler.

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 values need not be described, and for a single-parameter geo lookup the description covers what, where, and cost. It could be slightly richer on title-number format, but is adequate for correct invocation.

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 description coverage is 0%, so the description must carry the burden. It partially does by clarifying that title_number is an HMLR title number in England & Wales, but gives no format example or validation hints, leaving the single parameter only loosely specified.

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 resource ('registered proprietor(s)') and the exact key it expects ('HMLR title number'), so an agent knows it returns ownership for a single title. It separates cleanly from the sibling ownership_by_company by virtue of the input dimension, though it never names that sibling explicitly.

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 geographic scope ('England & Wales only') is stated, which usefully rules out non-E&W titles, but there is no explicit when-to-use versus alternatives guidance (e.g., versus ownership_by_company or owner_profile). Usage is only implied by the input type.

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