Vapi Structured Output Creation

Build the smallest reusable post-call extraction that represents the user's actual downstream contract. Keep definition creation, assistant attachment, execution, and result retrieval separate: success at one stage does not prove the next stage occurred.

Source and Safety Rules

• Use the configured Vapi documentation MCP when available. Otherwise use current public Vapi API documentation and [API Examples](references/api-examples.md). Revalidate request fields and SDK methods before final implementation.
• Use a private Vapi API key only on a trusted server. Read it from VAPIAPIKEY; never print, request in chat, or embed it in source, client-side code, or examples.
• Never invent resource IDs, call IDs, extraction fields, enum values, data-retention requirements, or customer data.
• Do not enable compliancePlan.forceStoreOnHipaaEnabled unless the user explicitly requests it and confirms that the output cannot contain PHI or other sensitive data.
• Treat call transcripts, messages, tool results, and extracted values as sensitive customer data. Minimize what is logged or reproduced.

Procedure

1. Choose the output mode.

- For a schema, payload, review, or implementation example, return an artifact without calling Vapi. State that nothing was saved, attached, or executed. - For a reusable saved definition, use POST /structured-output only when the user asks to create or save it and credentials are available. - For a one-call experiment that does not need a saved definition, pass a transient structuredOutput to POST /structured-output/run with previewEnabled: true. - Treat attachment, detachment, and execution against existing calls as separate requested actions. Do not infer them from creation alone.

1. Define the extraction contract.

- Identify the downstream consumer, required fields, optional fields, allowed categories, formats, and behavior when evidence is absent or ambiguous. - Ask only for missing facts that materially change the schema. State safe assumptions for the rest. - Split unrelated outputs when they have different consumers, retention policies, or iteration cycles. Keep one output when the fields form one stable business record.

1. Choose AI or regex.

- Use type: "ai" for meaning, classification, summarization, sentiment, outcome detection, normalization, or facts expressed in varied language. - Use type: "regex" only for deterministic transcript matching with a stable pattern. Use RE2-compatible syntax and choose a top-level schema type that matches the documented regex result: boolean, string, number/integer, or array. - Do not use regex to infer meaning. Do not use AI when a literal, stable pattern is the entire requirement.

1. Design the smallest useful JSON Schema.

- Include only fields the caller can provide or the call evidence can support. - Add concise descriptions that distinguish semantically similar fields. - Use enum for a closed category set, format or pattern for externally validated strings, and numeric bounds when the business contract defines them. - Mark a field required only when every valid call should produce it. Make conditionally available values optional instead of forcing guesses. - Prefer a primitive schema for a single value and an object only for a cohesive record. Avoid deep nesting unless the downstream contract needs it. - Validate the schema with a standard JSON Schema validator before sending it.

1. Create, inspect, or update the definition.

- Keep saved names between 1 and 40 characters. - On create, send name and schema; add type, description, regex, model, or compliancePlan only when intentional. - On inspect, resolve the exact resource with list filters or a verified ID, then use GET /structured-output/{id}. Do not guess from a partial name. - On update, read the current definition first and send only fields that should change. Use schemaOverride=true only when intentionally changing the schema's top-level type; otherwise do not use it to bypass schema safety. - Re-fetch after mutation and compare the requested fields. A successful HTTP status without the expected returned state is not verified success.

1. Attach or detach safely.

- Prefer the saved Structured Output's documented assistantIds relationship for attachment. Read its current assistantIds, add or remove exactly the resolved assistant ID, and preserve every unrelated ID. - Patch only assistantIds on the Structured Output for this operation. Re-fetch the Structured Output and assistant; verify the relationship and the assistant's artifactPlan.structuredOutputIds when returned. - If the implementation instead patches the assistant, first read the assistant and send the complete existing artifactPlan with only structuredOutputIds changed. Preserve recording, logging, transcript, scorecard, storage, and other artifact settings. - Do not claim that creating a definition attached it. Do not claim that detaching deleted it or removed results already stored on past calls.

1. Preview before broad execution.

- Use POST /structured-output/run with one real call ID and previewEnabled: true. Supply either structuredOutputId or a transient structuredOutput, not both. - Confirm the selected call contains representative evidence and that the returned value satisfies the schema and business meaning. - State that preview does not update the call artifact. - If extraction is wrong, simplify the schema or improve descriptions before changing models or custom extraction prompts.

1. Execute or backfill only when requested.

- Use previewEnabled: false or omit it to update call artifacts. Pass no more than the currently documented maximum of 100 call IDs per request. - Before a multi-call run, state the exact output, call count, and that existing values for this output may be replaced while other structured-output values remain. - Use only call IDs supplied by the user or returned by a verified public API query. Report partial failures by call ID; do not imply an all-or-nothing transaction.

1. Retrieve and verify results.

- After a normal attached call finishes, allow for post-call processing before checking the call. - Retrieve each call with GET /call/{id} and read call.artifact.structuredOutputs[structuredOutputId].result. - Validate the result against the intended schema and inspect representative source evidence before calling it accurate. Schema validity proves shape, not factual correctness. - Report separately: definition saved, assistant linked, preview returned, call artifact updated, and result validated. Mention only stages actually verified.

Error Handling

• On 400, inspect the response for schema, regex, model, relationship, or run constraints. Correct one unambiguous documented issue and retry once; never repeat an unchanged request.
• On 401 or 403, stop and report authentication or permission failure.
• On 404, report the missing Structured Output, assistant, or call and identify the exact unresolved ID.
• On 409, re-read current state before deciding whether the intended relationship or update already exists.
• On 429 or 5xx, preserve the request context, report the service condition, and do not claim success.
• If a result is absent, distinguish processing delay, missing attachment, disabled artifact storage, insufficient call evidence, and extraction failure before recommending a change.

API Implementation Examples

Read [API Examples](references/api-examples.md) when implementation code is needed. Use the official TypeScript or Python Server SDK only after confirming the generated method in its current official reference; use direct REST when SDK syntax is unavailable or unstable.

Output Contract

Return only the sections relevant to the request:

• Mode: artifact-only, saved definition, relationship change, preview, or artifact-writing run
• Assumptions or blocking questions
• Final schema and Structured Output configuration
• Created or updated resource ID and verified fields, when mutated
• Attachment state and preserved relationships, when changed
• Preview or execution result, affected call IDs, and whether artifacts changed
• Retrieved result plus schema and evidence limitations
• Remaining configuration or validation work

Public Sources

• Structured Outputs quickstart
• Create Structured Output API
• List Structured Outputs API
• Get Structured Output API
• Update Structured Output API
• Run Structured Output API
• Get Call API
• Official TypeScript Server SDK reference
• Official Python Server SDK reference