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

Beyond the annotations, the description discloses that the operation charges credits, mandates a specific flow version, and restricts what may be communicated to the user. These are useful behavioral constraints, though it does not discuss failure paths or insufficient-credit behavior.

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, each earning its place: the core action and side effect, the version/package sourcing rule, and the user-facing communication constraint. There is no filler or redundant restating of schema fields.

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?

The critical flow details (credits, version, packageId source) and messaging constraint are covered, and the presence of an output schema reduces the need to describe return values. But the required country/service semantics are absent, and 'Always use packageId' conflicts with packageId being optional in the schema.

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?

With only 20% schema description coverage, the description compensates for rentalFlowVersion and packageId by requiring version 2 and sourcing packageId from ucode_sms_rent_packages. However, it leaves required parameters country and service, as well as clientCredits, unexplained.

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 identifies this as the 'Primary rental' tool that charges Ucode credits, and the title adds 'Rent number (credits)'. The note about never mentioning wholesale/provider IDs distinguishes it from the provider-direct sibling. An agent can tell when this is the credit-based rental path.

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?

It gives concrete, imperative guidance: always use rentalFlowVersion 2 and take packageId from ucode_sms_rent_packages, matching mobile. It implies this is the default credit-based flow but does not explicitly state when to prefer it over ucode_sms_rent_provider_direct.

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