Enviar un mensaje de WhatsApp

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

Annotations already signal destructiveHint=true and readOnlyHint=false. The description adds critical behavioral details: it costs a credit (monetary cost), only works in sandbox with a test number, and returns a 'ref' for tracking. This goes beyond annotations by explaining the real-world impact and limitations.

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 verbose but packs important caveats (cost, sandbox, confirmation). It could be tightened without losing key information. The structure is front-loaded with action and cost, which is good, but the warnings add length.

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 5 parameters, no output schema, and the complexity of sending WhatsApp messages, the description covers essential aspects: return value (ref), cost, sandbox limitation, and the need for prior template approval. It is comprehensive for a send tool.

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 input schema already describes all parameters fully. The description adds minimal extra meaning beyond reminding that templateName must be 'exact' and variables follow a numbered scheme. This meets the baseline but does not significantly enhance understanding.

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 states the tool sends an approved WhatsApp template to a phone number. It specifies a single message (UNA plantilla), distinguishing it from broadcast tools like hilo_send_broadcast. The verb 'Envía' and resource 'plantilla de WhatsApp' are specific and unambiguous.

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 provides explicit context for use: it costs a credit, requires confirmation of recipient and content, and is sandbox-only (limited to test numbers). It mentions after-use verification via hilo_get_message. However, it does not explicitly state when to avoid this tool (e.g., for broadcasts) or provide direct alternatives beyond the return ref hint.

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