Create Rental

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

Goes well beyond the annotations by disclosing the difference between full-access and platform sourcing, the service-locking behavior, the 1/3/7-day duration restriction, and the refund terms. These are operational traits an agent cannot infer from readOnly/destructive hints alone.

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 dense sentences with no filler; the core distinction and prerequisites are front-loaded before the refund detail. Every sentence carries operational 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 mutating create operation with no output schema, it covers selection, prerequisites, tier constraints, and refund conditions well. The only notable gap is that it doesn't describe the return value or how to identify the newly created rental afterward, which would make it 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?

Schema coverage is already 100%, but the description adds tier-specific meaning, clarifies that platform is locked to one chosen service, and restates the allowed platform durations. It doesn't explain auto_renew behavior beyond the schema, but the added tier semantics justify above baseline.

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 first sentence uses a specific verb-resource pair ('Rent a phone number') and immediately distinguishes this tool from the one-off create_order sibling by contrasting extended rentals with single-use orders. It also defines the two tiers, so an agent knows exactly what operation this performs.

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?

Explicitly names create_order as the alternative for one-off numbers and states the preconditions: check rentals_available and rentals_price/rentals_pricing first. This leaves no ambiguity about when this tool should be selected over its closest sibling.

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