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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds real value beyond that: the required auth scope and, more importantly, the warning that user-authored text arrives under untrusted_fields and must be treated as display-only content rather than instructions. It does not describe the returned shape or not-found behavior, keeping it at 4 rather than 5.

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 short sentences, front-loaded with purpose, then the auth requirement, then the untrusted-content rule. The opening sentence only restates the title, but the remaining two are dense and high-value, so there is little waste.

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 one-parameter read tool with no output schema and rich annotations, the description supplies the pieces an agent actually needs: the permission gate and the prompt-injection handling rule. Only the lack of any return-content summary or error/not-found behavior keeps it from being fully complete.

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?

There is a single required parameter, invitation_id, with 0% schema description coverage, and the description adds nothing about its format or where an agent obtains one. The parameter name is largely self-explanatory, which keeps this at a minimum-viable 3 rather than lower.

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 names a specific verb and resource ('Get a booking invitation'), which is immediately distinguishable from siblings like get_booking_proposal, get_booking_event and claim_invitation. It stops short of explicitly contrasting with those siblings, so an agent must infer the invitation-vs-proposal distinction from the name alone.

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?

The only usage-adjacent information is the scope prerequisite 'Needs `bookings:read`'. There is no guidance on when to call this versus claim_invitation or get_booking_request-style siblings, and no statement about what happens if the caller lacks the scope or the invitation does not exist.

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