retell_create_phone_call

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

No annotations are provided, so the description must disclose behavioral traits on its own. It only states that a call is initiated and requires a purchased from_number; it does not describe whether the call is asynchronous, what the return value is, billing/side effects, or error behavior. This is insufficient for a side-effectful action.

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?

Two sentences, immediately states the core action, no filler. The second sentence covers prerequisites. Very efficient.

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?

Despite a well-covered schema, the tool has no output schema and no annotations, and it performs a side-effectful action (placing a call). The description is too brief to convey what happens after initiation, whether it returns a call object, or how it differs from related tools. It leaves significant operational context unexplained.

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 five parameters are documented in the schema with descriptions (100% coverage), so the description does not need to repeat parameter detail. The description adds minimal reinforcement that from_number must be purchased, which is already stated in the schema. Baseline 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 uses a specific verb ('Initiate') and resource ('outbound phone call via a Retell AI agent'), clearly conveying the action and distinguishing it from sibling tools like web calls and batch calls. It also identifies key prerequisites (purchased from_number, destination to_number).

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 context implies usage when the agent needs to make an outbound call with a purchased number, but it does not explicitly state when to use this instead of alternatives like create_web_call, create_batch_call, or register_phone_call, nor does it mention exclusions.

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