Check opt-out

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

Annotations already declare readOnlyHint=true and openWorldHint=true, and 'Read-only' merely restates them. The description does add one piece of real platform behavior — that sends to opted-out numbers are refused — but omits what happens on an invalid/unknown number and what the result looks like.

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, front-loaded with the core action, then the operational reason, then the safety profile. Nothing is padded or repeated.

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 read-only lookup with no output schema, the description should indicate the shape of the answer (boolean, status object, etc.) and it does not. With annotations covering the safety profile and only two simple parameters, the omission is a gap but not a severe one.

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 only 50%: the channel enum carries a description while phone_number only has a regex pattern. The description mentions 'a phone number' and 'a channel' but adds no format, default-value, or channel-selection meaning beyond what the schema already states.

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 (check) plus a precise resource (opt-out status of one phone number on a channel), which implicitly separates it from the sibling list_opt_outs. It never names an alternative sibling explicitly, so it falls short of the top band.

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?

'Vobiz refuses sends to opted-out numbers' supplies a rationale for checking, implying the tool is used before sending. However, it never states when to use this versus list_opt_outs, add_opt_out, or remove_opt_out, so guidance remains implied rather than explicit.

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