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

Annotations already declare the mutation, open-world, destructive, and non-idempotent profile, but the description adds genuinely non-obvious behavior: that this creates AND sends the trip invitation, that the user must have explicitly confirmed, and that a matching email reuses an existing traveler identity rather than creating a duplicate. It still says nothing about failure modes or required permissions.

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?

Four sentences, no padding, and the critical gating rule is front-loaded before the branch mechanics. Slightly dense but every sentence carries actionable 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 4-parameter mutation tool with no output schema, the description covers gating, side effects, and dedup behavior, which is enough to invoke it correctly. It omits any indication of what is returned or what happens to the record if the invitation send fails.

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% and the schema already documents name, email, trip_id, and invite_confirmed, including the conditional requirement on email. The description restates the email/invite_confirmed pairing without adding new format or value constraints, so a baseline 3 is appropriate.

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 concrete verb and resource ('Add a traveler') and immediately qualifies the scope with the invitation-decision flow, so the agent knows this creates trip membership and may send an invite. It does not explicitly contrast itself with nearby siblings like traveler_assign or traveler_update_email, which keeps it a step below a 5.

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 an explicit precondition (run/consult known_participants first, after the user's invitation decision) and spells out both branches: invite → email + invite_confirmed=true; decline → omit email + invite_confirmed=false. No alternative tool is named for the non-invitation path, so it falls short of full 'when/when-not/alternatives' coverage.

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