send_sms

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

No annotations provided, so the description fully bears the transparency burden. It discloses return fields (message_id, message_sid, status, credits_charged) and parameter effects, indicating a write operation with potential credit cost.

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?

Three short sentences, each serving a purpose: description, return values, parameter details. No fluff, and front-loaded with the core action.

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 description is sufficient for a straightforward SMS tool. It covers input format, optional parameter, and return values. Omits details like character limits or error handling, but given the presence of an output schema and the simplicity of the tool, it is reasonably complete.

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 0%, but the description adds E.164 format for 'to' and explains that phone_number_id is optional with auto-assignment. Could have specified body length limits or other constraints, but provides meaningful guidance beyond schema types.

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 'Send an SMS message' with a specific verb and resource. It distinguishes from siblings like send_email and other phone number management tools by focusing 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 implies when to use (sending an SMS) and provides parameter details, but does not explicitly mention when not to use or alternatives. The sibling set includes send_email, which is a clear alternative for different communication channels.

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