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

Annotations are minimal, so the description carries the behavior-disclosure burden. It states that this path skips the normal credit UX, uses upstream/provider balances, and exposes provider-era assumptions. This is a meaningful warning beyond what annotations already express, even though it does not detail balance debits or refund 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?

Two short sentences front-load the most important warning before any explanation. The alternative tool is named compactly, and the legacy rationale is compressed into a single clause with no redundant restatement.

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 description covers purpose, audience, and routing to the correct sibling, but omits guidance on valid country/service values and how to source them. An output schema exists, so return-value details are not a gap, but invocation semantics are still incomplete. This is adequate for a tool explicitly marked do-not-use, but not fully self-contained.

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 description coverage is 0%, and the description does not explain the country or service parameters. It only gives domain-level context about provider-balance rentals, which is not enough for an agent to know what values service expects or how country is used.

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 and title make it clear this tool rents a number using provider balance rather than credits. It explicitly labels itself as legacy and distinguishes itself from ucode_sms_rent_with_credits, so an agent can tell the operations apart without opening schemas.

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 opens with an explicit instruction: do not use for ChatGPT end users. It then names ucode_sms_rent_with_credits as the correct alternative with packages, giving a concrete routing rule.

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