whatsapp_get_contact

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

No annotations are provided, so the description fully carries the burden of transparency. It discloses that the tool relies on a sunset API (expired 2025-10-23), is not part of the Cloud API, and is retained only for backwards compatibility, effectively warning that it is not functional.

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 somewhat lengthy but every sentence is necessary to convey the legacy status, expiration date, and alternative approach. It is front-loaded with the core purpose and structured logically.

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 simple tool with one parameter and no output schema, the description is fairly complete. It explains the purpose, limitations, and alternative. It could be more specific about the exact error response, but the input schema's description already covers the return value.

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% with the schema describing the parameter and format. The description adds value by specifying E.164 format and stating that it returns 'WhatsApp ID and validity status', which enhances understanding beyond the schema alone.

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?

Description clearly states the tool performs a contact check on a phone number to verify WhatsApp account existence and retrieve the WhatsApp ID. It distinguishes from siblings by explicitly stating its legacy nature and that it is not part of the Cloud API, unlike other tools which are active.

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 tool is legacy/unsupported, not expected to work, and provides a clear alternative: send the message and inspect webhooks/error codes. This gives definitive when-to-use and when-not-to-use guidance.

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