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

Annotations flag destructive and open-world, and the description adds behavior beyond that: the precise handover sequence (announce to callee, ring user_phone_number, bridge both sides, then leave), the event lifecycle requested → ringing → connected/failed, and the critical fallback that on failure the voice agent stays on the line.

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?

Purpose and compliance rationale are front-loaded, and the operational sequence follows logically. It runs slightly long with a trailing line break and some redundancy between the failure clause and the event-progression sentence, but every sentence carries actionable content.

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 destructive, open-world handover tool with an output schema, this covers preconditions, side effects, failure handling, and post-call monitoring via get_call. Nothing an agent needs before invoking it 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?

Schema coverage is 100%, so both parameters are already documented, but the description adds meaning by tying user_phone_number to the ring step and call_id to 'the live call to hand over'. The French-only number format is left to the schema, which is acceptable given full coverage.

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 first sentence names a specific verb and resource: transferring a live call to the user's own phone so they can talk to the callee. It is unmistakable against siblings like place_phone_call or get_call, which neither transfer an existing live call nor target the user's own number.

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 explicit triggers ('recommended whenever a payment or sensitive data is needed'), explicit preconditions ('only when the user asked to take over... and can pick up their phone now'), an explicit failure condition ('Fails if the call is not in progress'), and routes progress-checking to get_call.

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