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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds real context beyond them: it is only a search handoff, it preserves the requested date, and it provides no live fares, availability, or tickets. That negative disclosure is genuinely useful for setting agent expectations.

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 tight sentences with the core purpose front-loaded and the key limitation last. Only the middle sentence about selecting dates on Omio is mildly redundant, but nothing is wasted.

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 read-only link generator with no output schema, the description covers purpose, the handoff workflow, and the crucial absence of live fares/tickets. Combined with fully documented params and safety annotations, an agent has everything needed to call it correctly.

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 all eight parameters (including trip_id/currency defaulting logic) are already fully documented in the schema. The description only alludes to dates and passenger details, adding nothing beyond the structured fields, so baseline 3 applies.

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 ('Return an Omio train-search handoff') and even narrows the supported routes (Madrid-Barcelona, Tokyo-Kyoto). This clearly separates it from flight_booking_link and ground_transfer_booking_links by mode, though it never names those siblings explicitly.

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?

Implies the use case (a handoff where the user finishes booking on Omio) and rules out expecting live data, but gives no explicit when-to-use vs alternatives routing against flight_booking_link or segment_booking_links. Usage is inferable rather than stated.

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