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

Annotations already flag destructiveHint=true, openWorldHint=true, and non-idempotency, so the safety profile is covered. The description adds genuinely new behavior: that passing email actually creates and sends the trip invitation to an external party, plus the dependency on known_participants. It does not address duplicate travelers or error/rollback behavior.

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 sentences, no filler, and the ordering constraint is front-loaded before the branching detail. It is slightly compressed but every clause carries information an agent needs at call time.

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 mutating tool with annotations present, no output schema, and fully documented parameters, the description covers the prerequisite, both decision branches, and the external send side effect. It omits what happens on success/failure or when the traveler already exists, which are minor gaps given the structured data available.

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%, so the schema already explains name, email, trip_id, and invite_confirmed, including the email/invite_confirmed coupling. The description largely restates that coupling in prose rather than adding new semantics, so the 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?

The description states a specific verb and resource ('Add a traveler') and immediately scopes it to the invitation workflow, setting it apart from sibling tools like traveler_assign, traveler_update_email, and known_participants. It stops short of explicitly naming the non-invitation alternative, so the differentiation is implied rather than stated.

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?

It gives a clear precondition ('only after known_participants and the user's explicit invitation decision') and spells out both branches: invite with email/invite_confirmed=true, or decline with invite_confirmed=false. No sibling alternative is named for adding a traveler without an invitation, so it falls short of a 5.

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