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

Annotations already cover read-only, idempotency and open-world behaviour, and the description adds real context beyond them: pricing (0.002 USDC via x402 or 1 credit), the free tier ('first 5 paid-tool calls a day are free'), and data provenance (Kadaster BAG via PDOK). It does not say what happens when no address matches or when a query is ambiguous, which matters for a geocoder.

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?

It leads with the trigger condition, then packs the returned fields, use cases, source and cost into compact clauses. Every clause carries either selection value or operational value (cost, free tier), and none is padding.

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, it usefully enumerates the returned fields, and it discloses the payment model and authoritative source. Missing pieces are how an unknown or ambiguous address is reported and which sibling to use for bulk or reverse lookups.

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 every parameter already carries an example, so the schema does the heavy lifting. The description's only addition is the framing 'postcode + house number or free text', which restates the 'Alternative to postcode' note already on q.

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 the specific verb and resource ('check that a Dutch address exists or get its exact spelling and coordinates') and lists concrete outputs (BAG ids, lat/lon, municipality, province, CBS neighbourhood code). Its input modes (postcode + house number or free text) implicitly separate it from nl_address_reverse and nl_address_batch, but it never names those siblings.

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 you need to check...' gives an explicit trigger, and the use cases 'onboarding, delivery and CRM' narrow the context. It stops short of exclusions, though: an agent is not told to switch to nl_address_batch for many addresses or to nl_address_reverse when starting from coordinates.

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