create_rental

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

No annotations are provided, so the description bears the full burden. It discloses that the tool creates a rental, the state determines billing start (ACTIVE begins billing immediately), and returns the rental with id and state. It does not mention authentication or rate limits, but the core behavior is clearly communicated.

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 concise: 4 sentences covering the main action, parameter constraints, optional fields, and return value. It is front-loaded with the core purpose, and every sentence adds value without redundancy.

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?

Given the tool has 6 parameters, no annotations, and an output schema, the description covers the essential behavioral context: creation, state-based billing, and return fields (id, state). It lacks error handling or prerequisites beyond signed-in user, but the output schema reduces the need to detail return structure. Overall it is fairly complete for a creation tool.

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 has 0% description coverage, so the description must compensate. It thoroughly explains all parameters: the mutual exclusivity of vehicle_id and vehicle_code, the meaning of start_rental_state, examples for additions (e.g., insurance, helmet), and the combination of user_group_code and rental_type='BUSINESS' for business billing. This adds significant meaning beyond the bare schema.

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 starts with 'Create a rental for the signed-in user', which is a specific verb and resource. It distinguishes from siblings like get_active_rental (read-only) and get_vehicles (listing) by clearly stating it creates a rental, optionally as a reservation or active rental.

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 gives clear parameter guidelines: 'Provide exactly one of vehicle_id or vehicle_code' and explains the start_rental_state options. It does not explicitly state when not to use the tool or compare with siblings, but the sibling names provide context. The guidance is sufficient for a typical use case.

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