retell_create_sms_chat

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

With no annotations, the description carries the full burden of behavioral disclosure. It only says 'Start an outbound SMS chat conversation' without revealing side effects (e.g., whether an SMS is immediately sent), error conditions, idempotency, or required preconditions. The one constraint it does mention ('using a phone number with SMS capability') is useful but insufficient for understanding operational behavior.

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, well-structured sentence that front-loads the verb and object. It contains no filler, repetition, or unnecessary detail. Every word contributes to the core purpose.

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 tool has 5 parameters and no output schema, the description provides only the minimal purpose. It doesn't clarify what the returned conversation object looks like, whether the chat is immediately active, or how it relates to sibling chat tools. For a simple 'create' operation this may be acceptable, but the lack of an output schema and annotations leaves gaps for an agent.

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?

The input schema covers 100% of parameters, so the description is not required to add details. However, the description adds zero extra context about parameters (e.g., that 'from_number' must be a Retell-owned number or that 'to_number' is the customer). The baseline of 3 is appropriate because the schema already communicates the essentials.

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 ('Start') and the resource ('outbound SMS chat conversation'), and specifies the requirement of 'a phone number with SMS capability'. This distinguishes it from sibling tools like retell_create_phone_call and retell_create_web_call, which handle different communication channels.

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 gives no explicit guidance on when to use this tool or how it compares to alternatives. It doesn't state prerequisites (e.g., need an SMS-capable number already configured) or situations where another tool would be more appropriate. This leaves the agent without clear selection criteria beyond the literal channel.

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