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

Annotations already cover read-only, idempotent, non-destructive and open-world behaviour, yet the description still adds material context an agent cannot get elsewhere: the RVO EP-Online provenance, the paid nature of the call (0.005 USDC via x402 or 3 API credits), and the free-tier allowance of five paid calls per day. Pricing and auth requirements are exactly the kind of disclosure the description is supposed to carry.

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?

Four tight sentences with a clear front-loaded 'Use when' clause, followed by input, provenance, and cost. Every sentence carries distinct information; nothing is repeated from the title or schema.

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?

For a read-only lookup with no output schema and all-optional parameters, the description compensates well by describing the returned fields and the 'none registered' fallback, plus the input expectation and cost model. An agent has everything needed to decide and call it correctly.

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 coverage is 100%, so every parameter including the free-text 'q' alternative and optional letter/addition fields is already documented. The description only restates 'postcode + house number', adding essentially no semantics beyond the schema, which is the baseline 3 case.

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: retrieves the officially registered energy label of a Dutch home, and enumerates the returned fields (label grade, registration/expiry date, building type, energy index). It does not explicitly differentiate itself from overlapping siblings such as nl_home_basic or nl_home_report, so it falls just short of a 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?

"Use when the user asks for the energy label of a Dutch home" gives a clear triggering condition, plus the required input (postcode + house number) and the source of truth. It offers no exclusions or named alternatives, so there is no guidance on when to pick nl_home_basic or nl_home_report instead.

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