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

Annotations already declare readOnly/idempotent/non-destructive, and the description goes beyond them by specifying the access method ('reads the public catalogue via GET requests'), the explicit absence of side effects ('does not create a cart, order or payment'), and the live nature of the data. Return contents (price, stock status, product link) are also disclosed, which annotations alone cannot convey.

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?

The English portion is front-loaded and efficient: purpose, when-to-use, return values, then side-effect disclaimer. The trailing Dutch sentence is a near-verbatim translation that adds no new information and slightly pads the definition.

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 correctly compensates by naming what comes back (current price, stock status, product link). Safety and side-effect expectations are covered and usage context is given. Minor gaps remain around result-count/pagination behavior and sorting, though the limit and sort parameters are documented in the schema.

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%, so every parameter is already documented with enums, bounds and defaults; the baseline is 3. The description reinforces the query parameter with illustrative subjects and mentions price range, but adds no syntax, format or edge-case detail beyond what the schema already supplies.

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 ('searches the live catalogue of Nummerschilderen.com for paint by numbers kits') plus the two facets it filters on (subject/keyword and price range). This clearly separates it from shop_info (shop metadata) and photo_size_advice (sizing help), so an agent can pick it without opening the schema.

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?

Provides explicit usage context ('Use when someone looks for a ready-made paint by numbers kit or a gift'), which is a clear trigger. It does not, however, state when not to use it or name the sibling tools (shop_info, photo_size_advice) as alternatives, so the routing guidance is implicit rather than complete.

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