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

No annotations are provided, so the description carries the full burden. It does disclose the 24-hour window constraint, which is the key behavioral trait and more than most definitions offer. However, it is silent on the failure mode when the window has expired, on rate limits, and on whether delivery is immediate or asynchronous — gaps that matter for a mutation tool with zero annotation coverage.

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?

One sentence, front-loaded with the action and ending on the constraint that governs whether the call will succeed. Nothing is padded or redundant.

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 all three parameters fully documented in the schema and no output schema required, the description only needs to convey the operating constraint, which it does. It falls just short of complete by not telling the agent what to do when the 24-hour window is not active.

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 description coverage is 100%, including E.164 format guidance for `to` and the default-sender behavior for `phone_number_id`, so the schema does the heavy lifting. The description adds no semantics beyond that; baseline 3 applies.

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?

A specific verb (send) plus resource (freeform WhatsApp text message) and recipient, with the qualifier 'freeform' implicitly distinguishing it from the sibling send_whatsapp_template. The agent can select this over send_sms and send_whatsapp_template without opening a schema.

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 'active 24-hour customer service window' clause gives one precondition, which is real usage context. But it never names the alternative route — e.g., that send_whatsapp_template must be used when the window is closed — which is the single most consequential routing decision for WhatsApp messaging. Usage is implied rather than directed.

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