Create Outbound Call

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

With no annotations provided, the description carries full burden for behavioral disclosure. It states the tool 'creates' a call, implying a write/mutation operation, but lacks details on permissions, side effects, error handling, or response format. The description doesn't address rate limits, authentication needs, or what happens after the call is fired.

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 appropriately brief (two sentences) and front-loaded with the core purpose. Every sentence serves a purpose: the first states the action, the second highlights key requirements. No wasted words, though it could be slightly more structured.

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 mutation tool with 8 parameters, no annotations, and no output schema, the description is insufficient. It doesn't explain what happens after the call is created, what the return value contains, error conditions, or important behavioral aspects. The description leaves too many contextual gaps for effective tool 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?

Schema description coverage is 100%, so the schema fully documents all 8 parameters. The description mentions only 2 parameters (phoneNumberId and customerNumber) and adds minimal context about E.164 format. It provides no additional meaning beyond what's already in the comprehensive schema descriptions.

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 specific action ('Fire an outbound call') and resource ('using a Vapi assistant'), distinguishing it from sibling tools like vapi_get_call or vapi_end_call. It precisely communicates the core function without ambiguity.

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 no guidance on when to use this tool versus alternatives like vapi_list_calls or vapi_end_call. It mentions required parameters but offers no context about prerequisites, timing, or exclusions for this outbound call operation.

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