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

Annotations already declare readOnly, idempotent and open-world behavior, so the safety profile is covered. The description then adds materially more: the data provenance (Kadaster BAG via PDOK) and the paid cost model (0.002 USDC via x402 or 1 Factline credit), which an agent needs before invoking a paid tool.

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?

Front-loads the purpose, then layers audience, source and pricing in a logical order. The first sentence is a long run-on list of return fields, but every clause carries information an agent needs.

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 enumerating the returned fields (distance, postcode, city, municipality, province, BAG ids, CBS buurt/wijk codes, nearby addresses). Combined with input format, source, and pricing, an agent has everything required to 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 the baseline is 3, but the description adds the coordinate system (WGS84), which the schema does not state. That is a genuine semantic addition beyond the example values in the schema.

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+resource (reverse geocoding of Dutch coordinates to official addresses) and names the exact standard (WGS84 in, BAG register out). It clearly distinguishes itself from sibling nl_address_lookup and nl_address_batch by name and by the reverse-geocoding direction.

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?

Provides clear usage context by naming target audiences (delivery, field service, mobility, real estate, mapping), which implies when the tool fits. It does not explicitly state when to prefer it over nl_address_lookup or nl_address_batch, so it stops short of full alternative routing.

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