Connect a new number

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

Annotations only provide false hints for readonly, idempotent, open-world, and destructive flags. The description adds valuable behavioral context: linking is billed, a new organization's first number is free, and the call 'starts' a linking flow rather than completing it instantly. This goes beyond the structured fields, though it does not describe failure or response behavior in detail.

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?

The description is dense but efficient: four sentences, all informative. It is front-loaded with the purpose and then gives the workflow, billing caveat, and alternative tool. Slightly longer than necessary, but no sentence is wasted.

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 6-parameter tool with a nested object and no output schema, the description covers the key context: how to choose proxyLocation, the two linking paths, billing consequences, and when to use create_invitation. It does not mention what the call returns or failure cases, but the schema fully documents all parameters and the workflow guidance is strong enough to invoke it correctly.

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 each parameter. The description adds extra meaning by tying proxyLocation to list_proxy_locations, explaining the QR-code versus pairingPhone choice, and noting the 8-character pairing code. This is meaningful value beyond the schema, though the schema remains the primary source for exact formats.

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 opens with a specific verb and resource: 'Start linking a new WhatsApp number.' It also distinguishes itself from create_invitation by explicitly saying that tool is for letting someone else link their own number, so an agent can tell them apart without inspecting schemas.

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?

The description gives a concrete workflow: pick proxyLocation via list_proxy_locations, then either show the QR code with get_account_qr_code or pass pairingPhone. It also names create_invitation as the alternative when someone else should link their own number, giving clear when-to-use guidance.

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