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

Annotations already declare readOnly/idempotent/non-destructive, so the description's real contribution is the commercial layer: 0.003 USDC via x402, 2 credits, and the first 5 paid calls per day free with no key. It also names the data provenance (Politie open data, CBS). It stops short of disclosing data recency, error behaviour for unknown postcodes, or rate limits beyond the free tier.

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 trigger phrase, then output content, then input, then source and pricing — a sensible order with no filler sentences. The payment sentence is dense and packs three separate cost mechanics into one clause, but each element is genuinely actionable for the caller.

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 naming the metrics returned and their form (counts plus ratio), which is enough for an agent to answer a safety question. The remaining gap is the zero-required-parameter design and the unstated behaviour when the postcode falls outside a known buurt.

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 both properties carry examples, so the description's "Input: Dutch postcode or CBS buurt code" is largely a restatement. Notably, required parameters are 0 and the schema presents these as alternatives without stating exclusivity, and the description doesn't clarify what happens if both or neither are supplied — a gap that affects correct invocation.

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 (police-registered crime per 1,000 residents vs the national rate) and enumerates the breakdown (burglary, bicycle theft, vehicle crime, violence, vandalism) plus the output shape (counts and a ratio). This clearly separates it from neighbours like nl_neighbourhood or nl_neighbourhood_summary without needing their schemas.

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 whether a Dutch neighbourhood or postcode is safe" gives an explicit trigger condition and input type, which is stronger than most siblings. It does not, however, say when to prefer a sibling such as nl_neighbourhood_summary or what to do if the question is about general liveability rather than crime.

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