Send SMS

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

Annotations already indicate destructiveHint=true and idempotentHint=false. The description adds valuable behavioral details: the maximum recipient limit, geographic coverage, and that it returns per-recipient status and cost. No contradictions with annotations.

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 three sentences long, each serving a distinct purpose: what the tool does, its capacity and scope, and its return value. No wasted words, and the most critical information is front-loaded.

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 with three well-documented parameters and an existing output schema, the description covers the essential aspects: operation, capacity, geographic scope, and return format. It is sufficiently complete for an agent to understand and use the tool correctly.

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%, so the schema itself clearly documents all three parameters. The description adds no additional parameter-level meaning beyond what is in the schema (e.g., it mentions Unicode support which is already in the message description). Baseline score of 3 is appropriate.

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 via Africa's Talking, specifies the maximum recipients (1,000), mentions geographic coverage, and indicates return of per-recipient status and cost, distinguishing it from sibling tools like airtime_send or mpesa_stk_push which perform different operations.

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 clear context for when to use the tool (sending SMS to one or many recipients) and includes practical limits (1,000 recipients). It does not explicitly mention when not to use it or compare to alternatives, but the sibling tools are sufficiently different that no confusion arises.

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