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

Annotations already declare idempotentHint=true and destructiveHint=false, and the description adds real context beyond them: it does not approve the call, it preserves the original request, and it tells the agent to reuse the same version and number on retry. That is meaningful behavioral disclosure, though no auth/permission or state-effect detail is given.

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 trigger and followed by the two caveats that matter (no approval, retry semantics). The first sentence is slightly indirect but wastes no words.

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 described, and annotations cover the safety profile. Combined with the schema and retry note, the description gives an agent enough to invoke this correctly; only permission/prerequisite context is absent.

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 100%, so the schema already documents taskId, version, and destination fully. The description only echoes the country-code expectation for destination and the version-reuse rule, adding little syntax or format detail beyond the schema.

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 title plus description make the resource clear (the destination number on a call task), and the phrase "doesn't approve calling" distinguishes it from the approve_call sibling. However, the description itself never states the verb+resource plainly (e.g. "sets the call destination"), relying on the title to carry the action.

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 implies the trigger condition (the owner answered "Who should we call?" with a number) and gives retry guidance ("Retry a lost reply with the same version and number"), which is genuinely useful. But it never names an alternative tool or an explicit when-not, so the routing is only implied.

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