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

With no annotations, the description does real work: it discloses that the tool only builds a URL (no booking is made server-side), that the transaction happens on the site with no credit card, no deposit, and free cancellation. The main gap is that it says nothing about URL lifetime or whether dates outside booking hours cause an error versus a degraded link.

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?

Three short sentences with the deliverable front-loaded, then the handoff consequence, then the one non-obvious parameter rule. Nothing is repeated from the schema and no sentence is filler.

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?

For a simple four-parameter URL builder with no output schema, this is nearly complete: what it returns, what happens next, and the language rule are all covered. The only missing piece is failure behavior for invalid or out-of-hours dates, which the schema hints at but never explains.

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 the schema already documents all four parameters including enums and the date-time pattern. The description adds only a small bit of meaning — that 'lang' should match the visitor — and says nothing about 'currency' or about the booking-hours constraint beyond restating the schema.

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 deliverable ('Builds a prefilled ... booking URL') plus the exact domain/path of the URL produced. An agent can immediately tell this is URL-construction, not a booking action or an availability/pricing lookup like its 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?

Usage is implied rather than stated: 'The visitor picks a car and confirms' tells the agent the flow is handed off, and the language-matching instruction gives a situational rule. But it never says when to use this versus check_car_availability or list_prices, nor whether availability should be confirmed first.

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