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

Annotations already declare readOnly, idempotent, non-destructive, and non-open-world behavior, so the safety profile is covered. The description adds genuinely new operational context: 'UK only' (a geographic constraint) and 'Costs 30 credits' (a consumption cost the agent should weigh before calling). The remaining gap is that it does not explain result shape or volume, though an output schema exists.

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 blocks, with the defining criterion front-loaded, then the differentiator, then the practical constraints. No sentence is redundant and nothing is buried.

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?

The output schema removes any need to describe return values, and the cost and UK-only constraints are disclosed. However, with four parameters at 0% schema coverage, an agent cannot determine what area_id accepts or how the min_* thresholds shape results, leaving a real gap for a filtered-query tool.

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 all four parameters (limit, area_id, min_commercial, min_residential) rely on the description, which never mentions them. The phrase 'BOTH residential and commercial' faintly implies the min_residential/min_commercial thresholds and their default of 1, but the area_id scoping, limit cap, and unit-count semantics are entirely undocumented.

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 precise, distinctive resource class: 'Buildings holding BOTH residential and commercial units.' The clarification that this is 'a property of the building's unit mix, not an attribute of any single property' separates it from property-level siblings (property_lookup, commercial_property) without naming them explicitly, which is why it lands at 4 rather than 5.

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?

No explicit when-to-use, when-not-to-use, or named alternative appears. 'Hard to source elsewhere' is a hint at uniqueness but not actionable routing guidance, and no sibling like commercial_property or sourcing_commercial is offered as a contrast. The agent must infer the use case from the resource definition alone.

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