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

Annotations cover the safety profile (readOnlyHint=true, destructiveHint=false), but the description adds genuinely non-derived operational context: the value is masked, and a voice-verified number is required rather than SMS-only login. It does not describe failure modes when no number is set beyond pointing at setup_url, which keeps it from a 5.

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?

Four short sentences, each carrying a distinct load: what is checked, what counts as verified, how the user configures it, and where to send them if it is missing. The purpose is front-loaded with no filler.

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?

With an output schema present, return values need no explanation, and the description covers the remaining agent-relevant concerns: prerequisite verification, masking, and the remediation path. Nothing needed to act on the result is missing.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; the baseline for a parameterless tool applies. No parameter-level confusion is possible here.

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 — checking where call_me would ring — and ties it to the sibling tool call_me rather than describing a generic status check. It also implicitly separates itself from caller_id_status by noting the receiving number is distinct from outbound Caller ID.

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?

Explicitly states the prerequisite (a number must be explicitly selected and verified by voice, and SMS login alone does not qualify), the interaction context (user can set it in the web app), and the fallback action (direct them to setup_url when no receiving number is ready). This is close to a complete when-to-use/when-not guide.

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