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

Annotations already declare this is a non-read-only, non-idempotent, non-destructive, open-world operation, and the description adds useful beyond-schema facts: per-message pricing ($0.004/msg), the pre-approved template constraint, and the returned confirmation fields. The significant omission is the non-idempotency risk: nothing warns that retrying a send may dispatch duplicate messages or calls, which is exactly the behavior an agent most needs disclosed for a costly outbound action.

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?

A single dense paragraph that front-loads the four actions before use cases and return values; every sentence carries information. It is tightly packed rather than padded, though the sentence is long and would scan faster if the action list and use-case list were separated.

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 correctly compensates by summarizing return values (dispatch confirmation, messageId, E.164 numbers, per-message cost). For a multi-action tool with 7 parameters, the gaps are behavioral rather than structural: no rate limits, no idempotency warning, and no statement of what the `logs` action returns relative to the dispatch actions.

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%, and each parameter is already documented in the schema, including required-combination notes for toNumber, templateName, and voiceScriptOrAgentId. The description reinforces the action-to-parameter mapping in prose but adds no format, constraint, or interaction detail beyond the schema, so the baseline of 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?

The description names specific verbs and resources for each mode: transactional SMS, WhatsApp Business Cloud template dispatch, outbound AI voice calls, and telecom usage ledger audit, each tied to its action value in backticks. The purpose is unmistakable. It does not explicitly contrast itself with the sibling telecom_numbers tool, which manages numbers rather than sending, so it falls just short of full sibling differentiation.

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?

Concrete use cases are given: out-of-band customer notifications, executive alerts, appointment reminders, autonomous voice follow-ups. It also states that WhatsApp messages must be pre-approved templates, which is a real prerequisite. However, it offers no when-not guidance and no explicit alternative routing (e.g., when to use telecom_numbers instead for provisioning).

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