send_sms

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

With no annotations, the description carries the full burden of disclosing side effects. 'Send' implies a mutating operation, but there is no mention of costs, delivery guarantees, idempotency, or potential failures. This leaves agents uncertain about consequences.

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, clear sentence with no unnecessary words. It is front-loaded with the core action. However, it sacrifices useful detail for brevity, slightly lowering the score from a perfect 5.

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?

Given the high number of parameters (18) and lack of output schema or annotations, the description is too minimal. It fails to explain essential behavioral traits (e.g., how 'to' handles multiple numbers, what 'debug' does, rate limits). More context is needed for safe and effective use.

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 18 parameters have descriptions in the input schema, providing solid coverage. However, the tool description adds no extra context beyond the schema. A 3 is appropriate when schema descriptions are comprehensive but the description doesn't enhance understanding.

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 action ('Send') and resource ('SMS message'), and hints at multiple recipients. This differentiates from sibling tools like send_rcs and send_voice, but could be more explicit about additional capabilities like scheduling or binary messages.

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?

No guidance on when to use this tool versus alternatives, no prerequisites (e.g., balance, sender validation), and no notes on constraints like rate limits. Agents must infer from the parameter schema alone.

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