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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuinely useful behavior beyond that: the underlying data source (Energy Performance Certificate) and a result cap of 'Up to 12 candidates', which affects how the agent should interpret coverage. It omits what happens when no EPC record exists, so not a 5.

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?

It is a single front-loaded sentence that leads with the primary output and then layers the secondary fields. The middle clause ('with what that era means for the construction, plus...') is somewhat dense and could be broken up, but nothing is wasted.

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 no output schema, the description does its job by enumerating the returned fields and the candidate cap. For a one-parameter read-only lookup, that is close to sufficient; only the no-match or missing-certificate behavior is unaddressed.

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 100% with a single required 'query' parameter already documented as 'Address or street with postcode'. The description's phrase 'homes matching an address' only loosely restates that and adds no format or matching semantics. Baseline 3 applies since the schema carries the parameter burden.

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 names a specific resource (construction age band from the EPC) and enumerates the extra fields returned: era interpretation, first recorded sale year, and property type. It is distinguishable from siblings like energy_performance or sale_history because it packages the age band with corroborating sale data. It does not explicitly say how it differs from those siblings, which keeps it 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?

Usage is only implied: the agent can infer it should call this when it wants to know when a home was built, and the 'matching an address' phrasing hints at the input. There is no explicit when-to-use/when-not guidance and no named alternative such as energy_performance or sale_history for related questions. Adequate but leaves routing to inference.

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