send_sms

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

With no annotations, the description carries the behavioral disclosure burden. It mentions sandbox mode behavior (no real send, no credit consumption) and character limits. But it does not discuss error handling, return values, or potential side effects like billing for real sends.

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 a single paragraph but remains concise and covers key points. It could be more structured (e.g., bullet points), but it is not verbose and front-loads the essential information.

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?

The tool has no output schema, but the description does not explain what the tool returns (e.g., success status, message ID). Given the complexity of 8 parameters and no output description, it lacks completeness for a sending 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 baseline is 3. The description adds value by explaining that numbers should be without country code, clarifying the message length context (1600 chars = 10 segments), and detailing the date format (Mexico time) and flash/SMS semantics.

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 SMS messages via SMS Masivos, specifying required elements (phone numbers, message, country code). It differentiates from siblings like send_payment_request and get_contacts by its specific focus on SMS sending.

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 guidance on using sandbox='1' for testing without real sending and notes the default country code (52 for Mexico). However, it does not explicitly list when to avoid using the tool or alternatives among siblings.

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