check_in

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It only mentions availability timing but fails to disclose that check-in is a mutation that modifies the reservation, may generate a boarding pass, or could fail if already checked in. This leaves critical side effects undocumented.

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?

The description is two concise sentences with the primary action front-loaded. Every word earns its place, and it avoids redundancy with the schema.

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?

While the description covers purpose and timing, it lacks information about preconditions (e.g., having an active reservation), effects, or return value. Given the absence of an output schema and annotations, more detail is needed for a fully self-contained tool description, though it is minimally viable.

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?

The input schema provides 100% coverage with clear descriptions for both parameters ('Passenger last name' and 'The 6-character confirmation code'). The description adds no parameter-specific information, so the baseline of 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 clearly states the specific action with a verb and resource: 'Complete online check-in for an American Airlines flight.' This distinguishes it from sibling tools like get_boarding_pass or select_seats, and the airline specificity adds useful context.

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 description provides a clear temporal guideline ('Available starting 24 hours before departure'), which tells the agent when to use it. However, it does not explicitly mention alternatives or when not to use it, though the context is strong enough for a 4.

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