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

Annotations already convey non-read-only and destructive side effects, and the description adds the window-independent behavior. However, it does not disclose billing implications, template approval prerequisites, or what happens on failure, which would be useful given destructiveHint=true.

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?

Two concise sentences: the first states purpose, the second adds the key behavioral qualifier. No filler, front-loaded, and every word earns its place.

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 no output schema, the description does not explain confirmation, response, or error behavior. It provides enough for basic invocation but lacks full operational context, and it does not explicitly differentiate from send_whatsapp_text beyond the template nature.

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 input schema provides 100% coverage for all four parameters with descriptions, so the description adds no additional parameter semantics. The baseline of 3 applies because the schema carries the explanatory burden.

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 clearly identifies the action ('Sends') and the resource ('pre-approved Meta WhatsApp template message'), with an explicit behavioral qualifier that it is window-independent. This distinguishes it from the sibling tool send_whatsapp_text, which likely handles regular in-session messages.

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 explicitly states when to use this tool: it can be sent proactively outside the 24-hour session window. It does not name an alternative or explicitly state when not to use it, but the window-independent note gives clear usage context.

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