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

Annotations only state the safety profile (write, non-destructive), so the description earns credit for disclosing copy semantics: everything (destinations and options) is carried over and the source variant is preserved. It stops short of noting that repeated calls create additional variants (idempotentHint=false) or what identifier comes back for follow-up selection.

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?

Two sentences, front-loaded with the action and scope, followed by the usage trigger with illustrative examples. No filler and every clause carries information.

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 two-parameter creation tool with no output schema, the description covers what is copied and why, which is enough to invoke it correctly. The one real gap is the return value (presumably the new variant id needed for select_variant), which has no output schema to fall back on.

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% and both tripId and variantId are documented in the schema with sourcing hints (list_trips, get_trip). The description only indirectly gestures at the same-trip constraint and adds no format or sourcing detail beyond the schema, 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 ('Copy a variant ... into a new variant on the same trip') plus the scope of what is copied (destinations and options). It implicitly distinguishes itself from the sibling create_variant by framing the action as a copy of an existing variant rather than creating a blank one, but it never names that sibling 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?

Gives a clear when-to-use condition with concrete examples ('same trip but a week later', 'same route, cheaper hotels') and the motivation ('without losing the original'). It does not name or exclude alternative tools such as create_variant or update_variant, so routing is still partly inferential.

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