send_a2p_sms

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

No annotations are provided, so the description carries full burden. It discloses that the action incurs charges, actually sends messages, and requires user confirmation. It does not mention the return format or potential side effects like history storage (though store_body parameter hints at it), but for a billing-sensitive tool, the payment warning is strong behavioral transparency.

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, dense sentence that front-loads the critical payment warning, then specifies the action and constraints. Every element adds value—no fluff, no repetition of schema data. The warning pyramid (danger first, then specifics) is effective for an agent.

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?

For a tool that performs a paid mass SMS send, the description covers the key actionable information: the billing implications, the need for explicit user confirmation, recipient limit, and the required context. There is no output schema, but the description doesn't need to explain return values for this use case. An agent can safely decide whether to call it and how to proceed with user confirmation.

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?

All parameters have schema descriptions covering 100% of the schema. The description itself adds no additional parameter semantics beyond what the schema already provides. Per rubric, baseline 3 is appropriate when schema coverage is high and the description doesn't need to compensate.

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 ('mass A2P SMS distribution'), the resource (via registered SenderID), and a clear scope (up to 100 recipients). It distinguishes this from regular SMS by emphasizing the A2P channel and bulk nature, and the sibling 'send_sms' is implicitly differentiated by the mass vs. single-message context.

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?

Explicitly provides when-to-use guidance: must confirm numbers and text with the user before calling, and explicitly forbids automatic invocation. It also implies this is a paid operation, which is critical context for when this tool should be chosen over non-billed alternatives.

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