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

Despite readOnlyHint=true and openWorldHint=true, the description adds significant behavioral context: it returns live starting prices, explains the marketplace, provides a direct link for fixed-price offers from verified carriers, and clarifies that prices are not final quotes. This pricing disclaimer explicitly states that the exact price is fixed only when the traveller picks an offer, which aligns with the read-only annotation and adds value beyond it.

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 dense and structured across four sentences, covering purpose, inputs, outputs, usage, and pricing. Each sentence adds information, but the enumeration of transfer types in the first sentence could be slightly tightened without losing clarity. It is efficient overall and front-loaded with the main purpose.

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 takes on the burden of explaining return values. It does so clearly: 'returns live starting prices by vehicle class for that route, how the transfer marketplace works, and a direct link to get fixed-price offers from verified carriers.' It also covers the pricing caveat and the kind of inputs expected, making it sufficiently complete for a search/quote tool.

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 67%, with 'from' and 'to' described in the schema. The description reinforces these two parameters with clear examples ('Vienna airport', 'city center', 'Prague') and explains optionality. However, the 'passengers' parameter is not described in either the schema or the description, leaving its meaning and importance ambiguous. The description compensates partially but not fully.

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 it handles private transfers (airport transfer, taxi, private driver, city-to-city, minibuses) and lists specific examples. This distinguishes it from sibling tools like search_car_rentals and search_tours. The verb 'Books' is slightly overbroad, but the overall scope is explicit and unambiguous.

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 ends with 'Use for any request to book a transfer, taxi or driver pickup,' which provides a clear trigger for when to invoke the tool. However, it does not explicitly mention when not to use it or name alternative tools, so while the context is clear, exclusions are absent.

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