Vapi
Vapi is a San Francisco-based voice AI platform that lets developers build real-time, low-latency voice agents over phone, web, and SIP. It orchestrates three modular components — a transcriber (STT), an LLM, and a voice (TTS) — into a sub-700ms voice-to-voice pipeline, with first-class support for tools/function calling, multi-agent squads, outbound campaigns, persistent sessions, structured outputs, recording artifacts, evaluation scorecards, and a full REST API plus official SDKs in TypeScript, Python, C#, Ruby, PHP, and client SDKs for Web, React Native, iOS, and Python. Vapi is a Y Combinator company.
Reference-quality API operations across every facet — a rich contract, published governance, transparent operations, and machine-readable commercial terms.
API Evangelist profiles Vapi the way a machine reads it — 121 machine-readable artifacts across 15 APIs, pulled from the provider's own public surface and indexed so a developer, an analyst, or an AI agent can evaluate it against every other provider on the network.
Every provider in the network is reduced to the same set of machine-readable artifacts — OpenAPI contracts, event specifications, GraphQL schemas, runnable collections, pricing and rate-limit signals, security posture, OAuth scopes, and the agent surfaces (MCP servers and skills) that let software drive the API on its own. We profile them because the interface is the part of a company you can actually inspect: it is a truer signal of what a provider does than any marketing page. From those artifacts we compute the Kin Score — Vapi scores 75.4/100 (exemplar), with a separate agent-readiness read of 84/100 (agent native). The full breakdown is below, followed by every artifact we hold — each card links through to its machine-readable definition on apis.io.
Kin Score
This is the API Evangelist rating — a single, repeatable read computed from the artifacts on this page. Green fill is points earned; the red track is points possible, so every bar shows earned-versus-possible at a glance.
How we profile Vapi
Each block below is one kind of artifact we hold for Vapi. For each we say what it is and why it earns a place in the profile, then list every one we've indexed — capped at two rows, scroll within the panel for the rest.
APIs 15
Each API is captured as its own OpenAPI definition — every operation, parameter, and response. This is the single most useful machine-readable description of what an API does, and it's what lets us score, lint, mock, and generate against it without asking the provider for anything.
Individual APIs this provider publishes, each with its own machine-readable definition.
Vapi Analytics API
Analytics endpoints.
Vapi Assistants API
Assistants endpoints.
Vapi Calls API
Calls endpoints.
Vapi Campaigns API
Campaigns endpoints.
Vapi Chats API
Chats endpoints.
Vapi Eval API
Eval endpoints.
Vapi Files API
Files endpoints.
Vapi Insight API
Insight endpoints.
Vapi Observability/Scorecard API
Observability/Scorecard endpoints.
Vapi Phone Numbers API
Phone Numbers endpoints.
Vapi Provider Resources API
Provider Resources endpoints.
Vapi Sessions API
Sessions endpoints.
Vapi Squads API
Squads endpoints.
Vapi Structured Outputs API
Structured Outputs endpoints.
Vapi Tools API
Tools endpoints.
Scroll within the panel for all 15 ·
Postman Collections 15
A runnable collection turns the contract into something a developer can execute in seconds. We profile them because the fastest way to trust an API is to make a real call against it.
Ready-to-run Postman collections for exercising this provider's APIs.
Vapi Analytics API
POSTMANVapi Assistants API
POSTMANVapi Calls API
POSTMANVapi Campaigns API
POSTMANVapi Chats API
POSTMANVapi Eval API
POSTMANVapi Files API
POSTMANVapi Insight API
POSTMANVapi Phone Numbers API
POSTMANVapi Provider Resources API
POSTMANVapi Sessions API
POSTMANVapi Squads API
POSTMANVapi Structured Outputs API
POSTMANVapi Tools API
POSTMANScroll within the panel for all 15 ·
Open Collections 15
Open, tool-agnostic collections carry the same runnable value as Postman without locking you to one client — the portable, forkable form of the same exercise.
Open, tool-agnostic API collections (OpenAPI-derived and Bruno).
Vapi Analytics API
OPEN COLLECTIONVapi Assistants API
OPEN COLLECTIONVapi Calls API
OPEN COLLECTIONVapi Campaigns API
OPEN COLLECTIONVapi Chats API
OPEN COLLECTIONVapi Eval API
OPEN COLLECTIONVapi Files API
OPEN COLLECTIONVapi Insight API
OPEN COLLECTIONVapi Observability/Scorecard API
OPEN COLLECTIONVapi Phone Numbers API
OPEN COLLECTIONVapi Provider Resources API
OPEN COLLECTIONVapi Sessions API
OPEN COLLECTIONVapi Squads API
OPEN COLLECTIONVapi Structured Outputs API
OPEN COLLECTIONVapi Tools API
OPEN COLLECTIONScroll within the panel for all 15 ·
Arazzo Workflows 8
Real integrations are rarely a single call. Arazzo describes the multi-step sequences — auth, then create, then confirm — so both a human and an agent can follow the choreography, not just the endpoints.
Multi-step API workflows described with the Arazzo specification.
Vapi Assistant Outbound Call End to End
Create an assistant, provision a Vapi phone number, place an outbound call, and poll until it ends.
ARAZZOVapi Build a Multi-Assistant Squad
Create two specialized assistants and assemble them into a squad that can hand calls between them.
ARAZZOVapi Outbound Call Then Cost Analytics
Place an outbound call, poll it to completion, then query call analytics for cost and duration.
ARAZZOVapi Create and Verify Assistant
Create a voice AI assistant and read it back to confirm it was provisioned.
ARAZZOVapi Create Function Tool and Attach to Assistant
Create a custom function tool and attach it to a freshly created assistant.
ARAZZOVapi File-Backed Knowledge Base Assistant
Upload a file, build a query tool knowledge base from it, and create an assistant that uses it.
ARAZZOVapi Import Twilio Number and Bind Assistant
Create an assistant and import an existing Twilio number that routes inbound calls to it.
ARAZZOVapi Squad Outbound Call
Build a two-assistant squad, place an outbound call to it, and poll until the call ends.
ARAZZOScroll within the panel for all 8 ·
MCP Servers 1
Model Context Protocol servers expose these APIs directly to AI agents. We profile them because agent-native access is the fastest-growing way this provider's capabilities actually get used.
Model Context Protocol servers that expose these APIs to AI agents.
vapi-ai-mcp.yml
MCP SERVERPricing Plans 1
Pricing is part of the interface. Machine-readable plans tell you what a tier costs and includes before you commit — one of the six things the Kin Score reads for commercial clarity.
Published pricing tiers and plan structures.
Rate Limits 1
Rate limits are the difference between a demo that works and a production integration that doesn't fall over. Publishing them is an operational-transparency signal — and a hard requirement for any agent that plans its own throughput.
Documented rate limits and quota policies.
Vapi Ai Rate Limits
RATE LIMITSFinOps 1
Cost, billing, and metering signals let a buyer model the financial operations of an API before it's live. We profile them for the same reason we profile pricing: the money is part of the contract.
Cost, billing, and metering signals for API financial operations.
Vapi Ai Finops
FINOPSFeatures 16
The notable capabilities this provider advertises, captured as structured features so they can be searched and compared instead of read one landing page at a time.
Notable capabilities this provider offers.
Scroll within the panel for all 16 ·
Event Specifications 1
Not every API is request/response. AsyncAPI describes the event-driven and streaming side — the webhooks and channels — so the asynchronous half of the interface is documented the same way the synchronous half is.
AsyncAPI definitions for this provider's event-driven and streaming APIs.
Vapi Realtime API (WebSocket Transport + Server URL Events)
AsyncAPI description of Vapi's realtime surfaces: 1. The WebSocket Transport (`wss://api.vapi.ai/{callId}/transport`) used to stream binary audio and JSON control messages to an...
ASYNCAPISemantic Vocabularies 1
JSON-LD contexts give the data shared meaning across APIs. We profile them because semantics are what let a machine reconcile 'customer' here with 'customer' somewhere else.
JSON-LD contexts and semantic vocabularies used across these APIs.
Vapi Ai Context
JSON-LDSpectral Rules 3
Governance rulesets we run against this provider's specs — the automated checks behind parts of the score. Profiling them makes the quality bar explicit and re-runnable, not a matter of opinion.
JSON Schema 13
Standalone JSON Schema definitions describe the data models behind the API. We profile them so the shapes are validatable on their own — useful long after a single request is forgotten.
Standalone JSON Schema definitions for this provider's data models.
Vapi Assistant
JSON SCHEMAVapi Call
JSON SCHEMAVapi Campaign
JSON SCHEMAVapi Chat
JSON SCHEMAVapi Eval
JSON SCHEMAVapi File
JSON SCHEMAVapi Insight
JSON SCHEMAVapi ByoPhoneNumber
JSON SCHEMAVapi Scorecard
JSON SCHEMAVapi Session
JSON SCHEMAVapi Squad
JSON SCHEMAVapi StructuredOutput
JSON SCHEMAVapi FunctionTool
JSON SCHEMAScroll within the panel for all 13 ·
JSON Structure 13
JSON Structure captures the data shapes in a form built for tooling — a complement to JSON Schema that keeps the model machine-legible.
JSON Structure definitions describing this provider's data shapes.
Vapi Assistant Structure
JSON STRUCTUREVapi Call Structure
JSON STRUCTUREVapi Campaign Structure
JSON STRUCTUREVapi Chat Structure
JSON STRUCTUREVapi Eval Structure
JSON STRUCTUREVapi File Structure
JSON STRUCTUREVapi Insight Structure
JSON STRUCTUREVapi Phone Number Structure
JSON STRUCTUREVapi Scorecard Structure
JSON STRUCTUREVapi Session Structure
JSON STRUCTUREVapi Squad Structure
JSON STRUCTUREVapi Structured Output Structure
JSON STRUCTUREVapi Tool Structure
JSON STRUCTUREScroll within the panel for all 13 ·
Examples 13
Real request and response payloads are what turn a spec from abstract into obvious — and they're one of the twelve things an agent needs to call an API correctly on the first try.
Example request and response payloads for these APIs.
Vapi Assistant Example
EXAMPLEVapi Call Example
EXAMPLEVapi Campaign Example
EXAMPLEVapi Chat Example
EXAMPLEVapi Eval Example
EXAMPLEVapi File Example
EXAMPLEVapi Insight Example
EXAMPLEVapi Phone Number Example
EXAMPLEVapi Scorecard Example
EXAMPLEVapi Session Example
EXAMPLEVapi Squad Example
EXAMPLEVapi Tool Example
EXAMPLEScroll within the panel for all 13 ·
Security Posture 3
Authentication, domain security, vulnerability disclosure, and trust-center signals — the evidence that a provider takes security seriously enough to document it. We profile it because you can't govern what you can't see.
Authentication, domain security, vulnerability disclosure, and trust-center signals.
Agentic Access 1
An x-agentic-access contract marks which operations are safe for an agent to run on its own and which need a human in the loop. It is the difference between an API an agent can use and one it can use safely.
Recommended x-agentic-access execution contracts for AI agents.
Resources
Every other property we hold for Vapi — documentation, portals, status pages, policies, and corporate surface — grouped by the job it does, following the integrator's arc from getting started to running in production.
Get Started 3
Portal, sign-up, and the first successful call
Documentation 5
Reference material describing how the API behaves
Agent Surfaces 4
MCP servers, agent skills, and machine-readable catalogs
Design & Contract 16
Pagination, idempotency, versioning, errors, and events
Scroll within the panel for all 16 ·
Build 18
SDKs, sample code, and the tooling you integrate with
Scroll within the panel for all 18 ·
Access & Security 4
Authentication, authorization, and security posture
Operate 5
Status, limits, changes, and where to get help
Commercial 6
Pricing, plans, and the legal terms of use
Company 3
The organization behind the API
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