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

Adds substantial behavioral detail beyond annotations: spends a credit, cannot be recalled, requires recipient consent, may require API Certification, and should be confirmed with the user. Annotations already declare destructive, non-idempotent, and open-world behavior, and the description enriches this with operational consequences.

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?

Front-loads the highest-risk information: real SMS, credit spend, irreversible. Each sentence adds a distinct operational warning or return detail, and the endpoint is listed cleanly at the end without waste.

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?

Despite no output schema, the description states the return identifiers. It covers consent, credit cost, irreversibility, confirmation guidance, and API Certification caveats, which is enough for an agent to call this destructive tool responsibly.

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 100%, so the schema already documents all five parameters thoroughly. The description reinforces that it sends one SMS to one mobile number with text, but adds no syntax or format detail beyond what the schema provides.

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?

States a specific verb and resource: sends one real SMS to one mobile number without adding the contact first. The scope phrase 'without adding the contact first' effectively distinguishes it from contact-adding siblings and from list-based messaging tools.

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?

Provides clear usage context: direct one-off SMS without contact creation, recipient consent required, possible API Certification, and confirmation with the user first. It does not explicitly name an alternative sibling or state when not to use it, so it falls short of a 5.

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