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

Annotations already declare readOnly/idempotent/safe, and the description adds genuinely non-redundant context: pricing (0.01 USDC via x402 or 5 credits), a free tier of 5 paid calls per day with no key, the upstream data sources, and that results are in English. None of that is recoverable from the structured fields.

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-loaded with the 'Use when' trigger, then input, sources, and cost — a sensible priority order. Dense and largely waste-free, though the long amenity/crime enumeration makes the first sentence heavy.

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 carries the return-value burden and does so thoroughly by enumerating every metric class and the output language. Payment mechanics, free tier, and accepted input types are all covered, leaving nothing an agent needs before calling.

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% and each parameter already carries its own example (postcode format, BU code format, api_key prefix). The description only restates that a postcode or buurt code is acceptable, adding no format, precedence, or edge-case guidance beyond the schema — baseline 3.

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?

Specific verb-plus-resource framing ('what a Dutch neighbourhood or postcode area is like') followed by an explicit content inventory: residents, age mix, housing, income, energy, amenities, crime, liveability. The one gap is that the clearly overlapping sibling nl_neighbourhood_summary is never mentioned, so the agent gets no explicit differentiation.

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' is a clear trigger condition, and 'Input: any postcode or CBS buurt code' scopes the accepted inputs. No when-not conditions and no named alternatives (e.g. nl_neighbourhood_summary, nl_crime, nl_house_prices) are offered.

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