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

Annotations already declare readOnly, idempotent, openWorld, non-destructive. The description goes beyond them with pricing behavior: 0.0015 USDC per address, 0.015 USDC via x402, 8 credits of a Factline key, first 5 paid calls per day free, and unfound addresses flagged but not charged. It does not cover rate limits beyond the free tier or response shape, which is why this is a 4 rather than a 5.

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 followed by scope, returned fields, then cost. Pricing is stated three ways (per-address, total, credits, free tier), which is slightly repetitive but each form serves a different agent decision.

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 it: it lists exactly what fields come back, describes the partial-failure case (unfound addresses flagged), and explains all payment paths. Nothing an agent needs in order to call this correctly is missing.

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 both parameters are already documented. The description adds meaning beyond the schema: the hard 10-address cap, the per-address cost implication, and that the energy label is optional via 'include'. It does not restate the ';' delimiter syntax, which the schema already covers.

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 and resource: enrich a list of Dutch addresses, up to 10 per call, and enumerates the returned data (BAG address, coordinates, CBS neighbourhood, liveability, crime, home value, optional energy label). The batch scope of 10 per call implicitly separates it from the single-address siblings like nl_address_lookup and nl_address_reverse, but no sibling is named explicitly.

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 enriching a list of Dutch addresses" is a clear trigger, and the 'include' note tells the agent when to request energy labels. It gives no explicit when-not or pointer to a named alternative (e.g. nl_address_lookup for one address, buy_full_address_report for a deep single report).

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