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

Annotations already declare destructiveHint=false, idempotentHint=true and readOnlyHint=false; the description adds real substance beyond them by specifying that existing/imported links are never changed or removed and that an identical URL is reported rather than duplicated. It also states what is returned. It stops short of permissions/auth or rate-limit context.

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?

Front-loads the purpose, then constraints, then the discovery workflow, then the return value — a logical ordering with little waste. It is a dense single paragraph, but each sentence carries distinct 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 no-output-schema mutation tool, the description covers scope, additive/dedupe semantics, the required segment-discovery workflow, and what is returned. An agent has everything needed to invoke it correctly without guessing.

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 the enum for link_type is fully documented in the schema, so the schema carries parameter meaning. The description's only added value is confirming the URL is separate from booking links; no new syntax or format guidance beyond 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 (add) and resource (a labeled, clickable URL) scoped to an 'ALREADY-EXISTING itinerary segment', with concrete examples (Menu, check-in, directions). This clearly separates it from sibling segment tools such as segment_booking_links or segment_update.

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 an explicit prerequisite workflow: call trips_list, then trip_details with sections ["segments"], match by title or venue rather than keyword search, then confirm with the user. It also states the additive constraint. It does not, however, name a sibling alternative (e.g. when to use a booking-link tool instead).

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