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

Annotations already declare idempotentHint=true, destructiveHint=false and readOnlyHint=false, so the safety profile is partly covered (note the oddity that a 'get' tool is not marked read-only, but the description does not contradict it). The description adds the four possible state values and the polling context for an in-flight verification, which is useful behavior beyond the annotations. It does not describe scoping of business_id or what happens when no caller ID is configured.

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 compact sentences with no filler, and the core meaning is up front. However, the first sentence is a sentence fragment, and enumerating the state values partly duplicates what the output schema already carries.

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?

An output schema exists, so return values need not be spelled out, and the description sensibly focuses on the verification workflow. The remaining gap is the undocumented, optional-looking business_id parameter and the absence of any note about the default scope, which matters for a multi-workspace caller-ID lookup.

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 single parameter business_id has 0% schema description coverage and the description says nothing about it — not whether it is required, what happens if omitted, or which workspace it scopes to. With one undocumented parameter, the description fails to compensate for the coverage gap.

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 states concretely what is returned: which outbound number is displayed (personal verified number vs. the KaiCalls line) plus the verification state. It is framed as an indirect question ('Which number Kai's outbound calls show') rather than a direct verb+resource statement, but an agent can still tell exactly what this retrieves and how it differs from the mutating siblings.

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 an explicit usage moment: call this to confirm a verification started with start_own_caller_id once the person has typed the code. That is real when-to-use guidance tied to a named sibling. It does not state exclusions (e.g., when to use set_ or remove_own_caller_id instead), which keeps it 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.