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

Annotations already cover idempotentHint, destructiveHint and readOnlyHint, but the description adds real value by spelling out the no-op behavior on repeat calls and confirming it runs without a confirmation step. It still doesn't say whether a check-in timestamp or audit entry is recorded, so not a 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 the action, then the idempotency behavior, then the risk posture. No sentence is redundant or padded.

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 single-parameter state-change tool with a complete schema and annotations covering safety and idempotency, the description supplies everything an agent needs to select and invoke it correctly.

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?

Only one parameter with 100% schema description coverage ('UUID of the participant to check in'), so the schema fully carries the semantics. The description adds no format or constraint detail beyond it, making the baseline 3 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?

States a specific verb and resource ('Mark a participant as checked in / arrived') and clarifies the operational moment it applies to. It is clearly distinguishable from siblings like assign_participant_to_session or check_trip_waiver_compliance, which change assignment or compliance rather than attendance state.

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 clear situational context ('typically at the point their waiver is verified in person'), which tells the agent when this fires in the workflow. It does not name alternative tools or state when NOT to use it, so it stops 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.