Get one marktplaats.nl listing

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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is known. The description adds useful behavioral context by detailing the exact fields returned (shipping carrier, counts, dates, etc.), which is not otherwise disclosed. It stops short of error-handling details, but the annotations lower the burden.

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 description is two sentences and quick to read. The first sentence states the core function, and the second lists the value-added fields. No unnecessary words or repetition.

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 listing the fields returned, giving the agent a clear idea of the response content. It doesn't mention error cases or the response format, but for a simple read-only fetch of a single resource, it is sufficiently complete.

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?

The input schema has 100% coverage for the single parameter 'listing', with a description explaining it can be an id or a full URL. The tool description merely repeats 'by id or URL' without adding new meaning, so it doesn't elevate beyond the baseline score.

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 clearly states the tool fetches full detail for a single listing by id or URL, and it distinguishes itself from search_listings by enumerating the additional fields it returns. The verb 'fetch' and the resource 'listing' are specific, making the purpose unmistakable.

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?

The description explicitly says it 'Adds what search does not carry,' which clearly informs when to use this tool instead of search_listings. This provides direct guidance on tool selection relative to a sibling tool.

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