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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.

agent native

Reference-quality API operations across every facet — a rich contract, published governance, transparent operations, and machine-readable commercial terms.

Kin Score

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.

Kin Score Kin Score How this is scored →
scored 2026-07-27 · rubric v0.5
Composite quality — 75.4/100 · exemplar
Contract Quality 19.2 / 25
Developer Ergonomics 15.2 / 20
Commercial Clarity 15.8 / 20
Operational Transparency 9.9 / 13
Governance 7.3 / 12
Discoverability 8.0 / 10
Agent readiness — 84/100 · agent native
Machine-Readable Contract 18 / 18
Agentic Access Contract 15 / 15
MCP Server 12 / 12
Machine-Readable Auth 10 / 10
Idempotency 0 / 9
Stable Error Semantics 8 / 8
Request/Response Examples 7 / 7
Rate-Limit Signaling 7 / 7
Typed Event Surface 6 / 6
Agent Skills 0 / 5
Well-Known Catalog 4 / 4
Consent & Bot Identity 0 / 3

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.

Scroll 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 COLLECTION

Vapi Assistants API

OPEN COLLECTION

Vapi Calls API

OPEN COLLECTION

Vapi Campaigns API

OPEN COLLECTION

Vapi Chats API

OPEN COLLECTION

Vapi Eval API

OPEN COLLECTION

Vapi Files API

OPEN COLLECTION

Vapi Insight API

OPEN COLLECTION

Vapi Phone Numbers API

OPEN COLLECTION

Vapi Sessions API

OPEN COLLECTION

Vapi Squads API

OPEN COLLECTION

Vapi Tools API

OPEN COLLECTION

Scroll 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.

ARAZZO

Vapi Build a Multi-Assistant Squad

Create two specialized assistants and assemble them into a squad that can hand calls between them.

ARAZZO

Vapi Outbound Call Then Cost Analytics

Place an outbound call, poll it to completion, then query call analytics for cost and duration.

ARAZZO

Vapi Create and Verify Assistant

Create a voice AI assistant and read it back to confirm it was provisioned.

ARAZZO

Vapi Create Function Tool and Attach to Assistant

Create a custom function tool and attach it to a freshly created assistant.

ARAZZO

Vapi File-Backed Knowledge Base Assistant

Upload a file, build a query tool knowledge base from it, and create an assistant that uses it.

ARAZZO

Vapi Import Twilio Number and Bind Assistant

Create an assistant and import an existing Twilio number that routes inbound calls to it.

ARAZZO

Vapi Squad Outbound Call

Build a two-assistant squad, place an outbound call to it, and poll until the call ends.

ARAZZO

Scroll 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 SERVER

Pricing 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.

Vapi Ai Plans Pricing

4 plans

PLANS

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

4 limits

RATE LIMITS

FinOps 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.

Features 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.

Sub-700ms voice-to-voice latency orchestration layer
Transcriber + LLM + voice (TTS) modular pipeline with multi-provider choice
Bring your own provider keys to pay providers at cost
Assistants, Squads (multi-agent handoff), Sessions (persistent state)
Inbound and outbound calling over Twilio, Telnyx, Vonage, vapi.phoneNumber, and SIP
Campaigns for batched outbound calling with concurrency/retry
Tools (function, transfer-call, end-call, DTMF, hangup, voicemail, MCP, query, Make, Zapier, GHL, KB)
Server URL webhooks for real-time call events and function execution
Per-call mono/stereo/customer/assistant/video recordings, PCAP packet captures, call logs
Analytics, Insights, Observability Scorecards, and Evals for production monitoring and regression testing
Structured Outputs for JSON-schema-constrained extraction from calls
Chats API (text channel) and OpenAI-compatible /chat/responses
Official SDKs - server (TS, Python, C#, Ruby, PHP) and client (Web, Python, React Native, iOS, HTML)
Vapi MCP Server for Model Context Protocol integration
HIPAA and Zero Data Retention add-ons; SOC2 and PCI on Scale plan
$0.05/min Vapi orchestration fee on Build plan; model and voice costs passed at cost

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...

ASYNCAPI

Semantic 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

0 classes · 12 properties

JSON-LD

Spectral 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.

Vapi API Rules

5 rules · 1 errors · 3 warnings

SPECTRAL

Vapi API Rules

5 rules · 3 warnings

SPECTRAL

Vapi API Rules

17 rules · 11 errors · 6 warnings

SPECTRAL

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

30 properties

JSON SCHEMA

Vapi Call

30 properties

JSON SCHEMA

Vapi Campaign

20 properties

JSON SCHEMA

Vapi Chat

18 properties

JSON SCHEMA

Vapi Eval

8 properties

JSON SCHEMA

Vapi File

18 properties

JSON SCHEMA

Vapi Insight

7 properties

JSON SCHEMA

Vapi ByoPhoneNumber

16 properties

JSON SCHEMA

Vapi Scorecard

8 properties

JSON SCHEMA

Vapi Session

20 properties

JSON SCHEMA

Vapi Squad

7 properties

JSON SCHEMA

Vapi StructuredOutput

13 properties

JSON SCHEMA

Vapi FunctionTool

12 properties

JSON SCHEMA

Scroll 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

30 properties

JSON STRUCTURE

Vapi Call Structure

30 properties

JSON STRUCTURE

Vapi Campaign Structure

20 properties

JSON STRUCTURE

Vapi Chat Structure

18 properties

JSON STRUCTURE

Vapi Eval Structure

8 properties

JSON STRUCTURE

Vapi File Structure

18 properties

JSON STRUCTURE

Vapi Insight Structure

7 properties

JSON STRUCTURE

Vapi Phone Number Structure

16 properties

JSON STRUCTURE

Vapi Scorecard Structure

8 properties

JSON STRUCTURE

Vapi Session Structure

20 properties

JSON STRUCTURE

Vapi Squad Structure

7 properties

JSON STRUCTURE

Vapi Structured Output Structure

13 properties

JSON STRUCTURE

Vapi Tool Structure

12 properties

JSON STRUCTURE

Scroll 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

8 fields

EXAMPLE

Vapi Call Example

8 fields

EXAMPLE

Vapi Campaign Example

8 fields

EXAMPLE

Vapi Chat Example

8 fields

EXAMPLE

Vapi Eval Example

8 fields

EXAMPLE

Vapi File Example

8 fields

EXAMPLE

Vapi Insight Example

7 fields

EXAMPLE

Vapi Phone Number Example

8 fields

EXAMPLE

Vapi Scorecard Example

8 fields

EXAMPLE

Vapi Session Example

8 fields

EXAMPLE

Vapi Squad Example

7 fields

EXAMPLE

Vapi Tool Example

8 fields

EXAMPLE

Scroll 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.

Vapi Ai Authentication

http · 1 scheme

SECURITY

Vapi Ai Domain Security

TLSv1.3 · HSTS · DNSSEC · DMARC

SECURITY

Vapi Ai Trust Center

SOC 2, PCI DSS, GDPR

SECURITY

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.

Vapi Ai Agentic Access

86 operations · 48 acting · 48 human-in-the-loop

86 operations · 48 acting

AGENTIC

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

Agent Surfaces 4

MCP servers, agent skills, and machine-readable catalogs

Company 3

The organization behind the API

← All providers · Data indexed from github.com/api-evangelist/vapi-ai · machine-readable index on apis.io