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

Annotations already declare readOnly, idempotent, openWorld and non-destructive behavior, but the description adds critical non-schema context: the Kadaster BAG/PDOK source, the exact cost (0.005 USDC via x402 or 3 credits), and the free-tier rule (first 5 paid calls daily). For a paid data tool, this is exactly the behavioral information an agent needs before invoking it.

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 sentences, front-loaded with the when-to-use clause, followed by field inventory, use cases, and the payment/source facts. Every sentence earns its place, and nothing is repeated from annotations 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?

With no output schema, the description correctly enumerates the key returned fields and sorting. It also covers source, cost, and free-tier access, which are essential for a paid open-world read tool. An agent has everything needed to decide to call it and to anticipate the response shape.

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%, and the single postcode parameter is already documented in the schema with format guidance ('6-character postcode, e.g. 2517AS'). The description adds only the word 'Dutch' and no syntax or normalization detail beyond the schema, so baseline 3 is appropriate.

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 specific verb and resource — 'every address in a Dutch postcode' — and enumerates the returned fields (street, house number, letter, addition, BAG id, coordinates, sorted). This is far more concrete than the title alone, though it never names the sibling tools it should be preferred over (e.g., nl_address_lookup or nl_address_reverse).

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?

It gives explicit usage conditions ('Use when you need every address in a Dutch postcode') and concrete scenarios (address pickers, delivery and canvassing routes, data cleaning). It does not state when not to use it or name the alternative for a single address, so sibling routing still requires inference.

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