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

With no annotations, the description carries the full behavioral burden and does disclose important constraints like scheduling exclusivity and the WABA 24-hour delivery window. However, it does not explain many action-specific behaviors, rate limits, authentication needs, or return behavior, leaving significant gaps for such a large tool.

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 front-loaded with purpose and scheduling rules, and the scheduling guidance is dense and useful. It has some mild redundancy in the opening paragraph, such as repeating that all message sending operations are unified, but it remains appropriately sized for a complex 22-parameter tool.

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?

Given the tool's complexity, 22 parameters, and no output schema, the description provides key operational context around scheduling and WABA delivery constraints. The schema itself thoroughly documents parameters, but the description does not explain return values or all action-specific behavior, so it is strong but not fully complete.

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 individual parameters. The description adds cross-parameter meaning by stating exactly one of deliverAt, delay, or delayTo must be used and that omission sends immediately, which is useful semantic context beyond the schema.

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 states a specific verb and resource: it sends WhatsApp messages and enumerates supported message types and actions. It does not explicitly differentiate itself from sibling sending tools such as send_whatsapp_flow or campaign/channel message tools, so it falls short of a 5 despite being otherwise clear.

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 strong when-to-use guidance for scheduling: pass exactly one of deliverAt, delay, or delayTo, and leaving all out sends immediately. It also explains the WABA 24-hour window and directs delayed reminders to the template action. It does not, however, explain when to choose this tool over sibling sending tools.

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