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

No annotations are provided, so the description must disclose behavioral traits. The only extra information is 'Billing per call: Credits: metered,' which hints at cost but is cryptic. It does not state side effects (e.g., sends an actual SMS, may incur charges), whether it is destructive (e.g., consumes credits), or any rate limits. The description is minimal and fails to carry the burden of transparency.

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 extremely short (one sentence plus a billing note). It is concise, but the billing note is incomplete and confusing ('Credits: metered' is not a standard phrase). There is no additional structure or bullet points; the description front-loads the purpose but fails to use the space effectively. Every word should add value, but much is wasted.

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 a single parameter, no output schema, and no annotations, the description should clarify behavior and edge cases. It only mentions metered credits, leaving out whether the SMS is actually sent, what the response contains, error conditions, and consent/privacy requirements. The tool is simple, but the description is incomplete for safe invocation.

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 only one parameter 'body' with a description that includes an example ('target': '+44...'), which already provides clear semantics (JSON request body with a target phone number). Since schema description coverage is 100%, the baseline is 3. The tool description adds no extra parameter information; it relies entirely on the schema. The example is helpful, so no deduction is made.

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 restates the tool name ('Send Verify SMS') without specifying the action beyond sending a verification SMS. It is not a tautology, but it is vague—no indication of what 'verify' means, what the SMS contains, or the scope (e.g., phone number verification). It does not distinguish from sibling (post_estimate_cost), as 'verify' likely refers to a verification code being sent. The purpose is under-specified. The description is a near-verbatim repetition of the title, offering no specific verb+resource.

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 provides no context on when to use this tool versus the estimate cost sibling. It does not mention typical use cases (e.g., sending a verification code during signup) or conditions under which it should not be used. It lacks any indication of alternatives or exclusions, leaving the agent without guidance.

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