Set Vapi structured outputs

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

Annotations (destructiveHint: false, idempotentHint: false) already signal safety and non-idempotency. The description adds the key behavioral detail that omitting definitions yields a specific template schema, which is beyond what annotations convey. It doesn't discuss side effects like whether existing outputs are replaced, but the openWorldHint softens this gap.

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, with the core action front-loaded. The first sentence names the operation and target; the second explains the default behavior without redundancy. Every word earns its place.

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 tool with 3 params and no output schema, the description covers the essential behavior but omits practical details like whether calling it multiple times accumulates or replaces outputs, or whether the client must already be provisioned. Given the tool's moderate complexity and sibling context, a bit more context on side effects would be valuable, though not critical.

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?

With 67% schema coverage, clientSlug and replaceLocalIds have descriptions, but outputDefinitions (the most complex parameter) only has an opaque item description. The tool description compensates by enumerating the template fields ('name, number, reason, callback window, transfer outcome'), directly informing agents what a default output would contain. This adds genuine meaning beyond the schema.

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 verb ('Create') and resource ('structured outputs attached to the client assistant'), and goes further to describe the default template behavior when no definitions are provided. This level of specificity distinguishes it from sibling tools like attach_tools or set_prompt_and_voice without requiring the agent to open the schema.

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 the tool by explaining the default template behavior, which gives context for when callers might omit outputDefinitions. However, it doesn't explicitly state when not to use it or name alternatives among sibling tools, leaving the agent to infer usage relative to set_prompt_and_voice or attach_tools.

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