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

On top of the annotations, the description discloses the full cost model (0.01 USDC via x402, or 5 Factline credits, first 5 paid calls per day free with no key), the underlying data sources (CBS, Politie, Leefbaarometer), and the response language (English). Cost and auth behavior is exactly the context annotations cannot convey, so this earns the top score.

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?

A single dense paragraph that front-loads the trigger condition and payload list before the practical details (inputs, sources, cost). Nothing is clearly redundant, though the pricing tail makes it longer than strictly needed for tool selection.

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 well by enumerating the returned data categories and the language of the result. What is missing is the failure mode when neither postcode nor code is supplied (both parameters are optional) and 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 both parameters carry their own examples, so the baseline is 3. The description's "Input: any postcode or CBS buurt code" adds only the mutual-alternative framing, not format or precedence rules for when both are supplied.

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 (Dutch neighbourhood / postcode profile) and enumerates the exact content returned: residents and age mix, housing values, income, energy use, amenity distances, crime vs national rate, liveability. That is far beyond a restatement of the name. It does not explicitly differentiate from the close sibling nl_neighbourhood_summary, which keeps it from 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 what a Dutch neighbourhood or postcode area is like" gives a concrete trigger condition, and the accepted inputs (any postcode or CBS buurt code) are stated. No alternative sibling is named or excluded, so routing between this and nl_neighbourhood_summary or nl_postcode_addresses is left to inference.

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