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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the safety profile is covered. The description adds genuinely new behavioral context the annotations do not: the data source (RVO EP-Online national register), a cost model (0.005 USDC via x402 or 3 credits of a Factline key), and the 'none registered' negative-result path.

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?

Dense but well front-loaded: the core lookup and data source lead, followed by audience, input, and cost. Every clause carries information, though the source and cost sentences could be tightened slightly.

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 compensates by specifying return fields and the negative-result case, and it discloses the source and pricing model. An agent has everything needed to decide to call it and interpret the result.

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%, so all five parameters are already documented in the schema, making 3 the baseline. The description's 'Input: postcode + house number' hints at the primary addressing path but actually understates the schema, which permits the free-text 'q' alternative with zero required params.

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 and resource — 'Netherlands home energy label (EPC, energielabel) lookup by address' — and enumerates exactly what is returned (label A++++ to G, registration/expiry date, building type, energy index, or a 'none registered' outcome). That level of specificity clearly separates it from generic siblings like nl_home_basic or nl_home_report.

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?

Names intended audiences (real estate, mortgage, green-finance, ESG, renovation agents) which gives implied usage context, but never names an alternative tool or states when NOT to use this one versus nl_home_basic / nl_home_report. Useful framing, but exclusions and sibling routing are absent.

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