Fixie website screenshot

Fixie

Fixie is the company behind Ultravox Realtime, a speech-native voice AI platform for building natural, low-latency conversational voice agents. Rather than transcribing speech to text first, Ultravox processes audio directly to preserve tone, cadence, and pitch while cutting latency. The Ultravox Realtime REST API (api.ultravox.ai) lets developers create reusable agents, start and manage calls, define custom and built-in tools, clone and manage voices, build RAG corpora, wire telephony (Twilio, Telnyx, Plivo, SIP), and subscribe to call-lifecycle webhooks. Client SDKs ship for JavaScript, Python, Flutter/Dart, React Native, Kotlin/Android, and Swift/iOS. Fixie was backed by Redpoint Ventures; fixie.ai now redirects to ultravox.ai and its open models are published under the fixie-ai organization on Hugging Face.

Fixie publishes 14 APIs on the APIs.io network, including accounts API, agents API, api_keys API, and 11 more. Tagged areas include Company, Voice AI, Conversational AI, Real-time, and Speech.

The Fixie catalog on APIs.io includes 1 event-driven AsyncAPI specification.

Fixie’s developer surface includes changelog, documentation, API reference, getting-started guide, engineering blog, pricing, signup flow, and 16 more developer resources.

🌐 Visit website 📡 Source on GitHub
52.3/100 developing ▬ flat Agent 28/100 agent aware Full breakdown ↓
scored 2026-08-10 · rubric v0.9.1
AccessSelf serve
14 APIs
CompanyVoice AIConversational AIReal-timeSpeechAgentsTelephonyMachine LearningSIPWebhooks

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-08-10 · rubric v0.9.1
Composite quality — 52.3/100 · developing
Contract Quality 14.4 / 25
Developer Ergonomics 9.9 / 20
Commercial Clarity 10.5 / 20
Operational Transparency 6.8 / 13
Governance 1.4 / 12
Discoverability 9.3 / 10
Agent readiness — 28/100 · agent aware
Machine-Readable Contract 18 / 18
Agentic Access Contract 10 / 10
MCP Server 0 / 12
Machine-Readable Auth 0 / 10
Idempotency 0 / 9
Stable Error Semantics 0 / 8
Request/Response Examples 7 / 7
Rate-Limit Signaling 0 / 7
Typed Event Surface 6 / 6
Agent Skills 5 / 5
Well-Known Catalog 0 / 4
Consent & Bot Identity 0 / 3
A2A Agent Card 0 / 8
Dry-Run / Simulate Mode 0 / 4
Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. This rating is computed from github.com/api-evangelist/fixie: open an issue to ask a question, or submit a pull request to add artifacts. Want it done for you? Prioritized profiling — $2,500 →

APIs 14

Individual APIs this provider publishes, each with its own machine-readable definition.

Fixie accounts API

The accounts API from Fixie — 9 operation(s) for accounts.

Fixie agents API

The agents API from Fixie — 9 operation(s) for agents.

Fixie api_keys API

The api_keys API from Fixie — 2 operation(s) for api_keys.

Fixie call_throttles API

The call_throttles API from Fixie — 2 operation(s) for call_throttles.

Fixie calls API

The calls API from Fixie — 13 operation(s) for calls.

Fixie corpora API

The corpora API from Fixie — 8 operation(s) for corpora.

Fixie deleted_calls API

The deleted_calls API from Fixie — 2 operation(s) for deleted_calls.

Fixie models API

The models API from Fixie — 1 operation(s) for models.

Fixie schema API

The schema API from Fixie — 1 operation(s) for schema.

Fixie sip API

The sip API from Fixie — 3 operation(s) for sip.

Fixie telephony_configs API

The telephony_configs API from Fixie — 3 operation(s) for telephony_configs.

Fixie tools API

The tools API from Fixie — 4 operation(s) for tools.

Fixie voices API

The voices API from Fixie — 4 operation(s) for voices.

Fixie webhooks API

The webhooks API from Fixie — 2 operation(s) for webhooks.

Scroll for all 14

Event Specifications 1

AsyncAPI definitions for this provider's event-driven and streaming APIs.

Fixie Webhooks

ASYNCAPI

Security Posture 3

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Fixie Authentication

apiKey · 1 scheme

SECURITY

Fixie Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Fixie Trust Center

trust center published

SECURITY

Agentic Access 1

Recommended x-agentic-access execution contracts for AI agents.

Fixie Agentic Access

114 operations · 57 acting

114 operations · 57 acting

AGENTIC

Resources

Get Started 4

Portal, sign-up, and the first successful call

DeveloperPortal
DeveloperPortal
 GettingStarted
GettingStarted
 SignUp
SignUp
 Login
Login

Documentation 2

Reference material describing how the API behaves

Documentation
Documentation
 APIReference
APIReference

Agent Surfaces 2

MCP servers, agent skills, and machine-readable catalogs

AgentSkill
AgentSkill
 LLMsTxt
LLMsTxt

Design & Contract 1

Pagination, idempotency, versioning, errors, and events

Webhooks
Webhooks

Build 3

SDKs, sample code, and the tooling you integrate with

Packages
Packages
 SDKs
SDKs
 GitHubOrganization
GitHubOrganization

Access & Security 2

Authentication, authorization, and security posture

DomainSecurity
DomainSecurity
 TrustCenter
TrustCenter

Operate 4

Status, limits, changes, and where to get help

ChangeLog
ChangeLog
 StatusPage
StatusPage
 Deprecation
Deprecation
 Support
Support

Commercial 3

Pricing, plans, and the legal terms of use

Pricing
Pricing
 TermsOfService
TermsOfService
 PrivacyPolicy
PrivacyPolicy

Company 2

The organization behind the API

Blog
Blog
 Website
Website

Source (apis.yml)

apis.yml Raw ↑ 
aid: fixie
name: Fixie
description: Fixie is the company behind Ultravox Realtime, a speech-native voice AI platform for building natural, low-latency
  conversational voice agents. Rather than transcribing speech to text first, Ultravox processes audio directly to preserve
  tone, cadence, and pitch while cutting latency. The Ultravox Realtime REST API (api.ultravox.ai) lets developers create
  reusable agents, start and manage calls, define custom and built-in tools, clone and manage voices, build RAG corpora, wire
  telephony (Twilio, Telnyx, Plivo, SIP), and subscribe to call-lifecycle webhooks. Client SDKs ship for JavaScript, Python,
  Flutter/Dart, React Native, Kotlin/Android, and Swift/iOS. Fixie was backed by Redpoint Ventures; fixie.ai now redirects
  to ultravox.ai and its open models are published under the fixie-ai organization on Hugging Face.
url: https://raw.githubusercontent.com/api-evangelist/fixie/refs/heads/main/apis.yml
x-type: company
x-source: vc-portfolio
x-backed-by:
- redpoint-ventures
x-tier: profiled
x-tier-reason: enriched-from-public-api
accessModel:
  pricing: unknown
  onboarding: self-serve
  trial: false
  try_now: false
  public: false
  label: Self-serve signup
  confidence: medium
  source:
  - authentication
  generated: '2026-07-22'
  method: derived
specificationVersion: '0.20'
created: '2026-07-17'
modified: '2026-07-19'
image: https://raw.githubusercontent.com/api-evangelist/fixie/refs/heads/main/openapi/fixie-ultravox-openapi-original.yml
tags:
- Company
- Voice AI
- Conversational AI
- Real-time
- Speech
- Agents
- Telephony
- Machine Learning
- SIP
- Webhooks
apis:
- aid: fixie:fixie-accounts-api
  name: Fixie accounts API
  description: The accounts API from Fixie — 9 operation(s) for accounts.
  humanURL: https://docs.ultravox.ai/
  baseURL: https://api.ultravox.ai/api
  tags:
  - accounts
  properties:
  - type: OpenAPI
    url: openapi/fixie-accounts-api-openapi.yml
  - type: Authentication
    url: authentication/fixie-authentication.yml
  - type: AgenticAccess
    url: agentic-access/fixie-agentic-access.yml
  - type: Conventions
    url: conventions/fixie-conventions.yml
  - type: ErrorCatalog
    url: errors/fixie-problem-types.yml
  - type: Lifecycle
    url: lifecycle/fixie-lifecycle.yml
  - type: DataModel
    url: data-model/fixie-data-model.yml
  - type: Conformance
    url: conformance/fixie-conformance.yml
  - type: AsyncAPI
    url: asyncapi/fixie-webhooks.yml
  - type: Webhooks
    url: asyncapi/fixie-webhooks.yml
- aid: fixie:fixie-agents-api
  name: Fixie agents API
  description: The agents API from Fixie — 9 operation(s) for agents.
  humanURL: https://docs.ultravox.ai/
  baseURL: https://api.ultravox.ai/api
  tags:
  - agents
  properties:
  - type: OpenAPI
    url: openapi/fixie-agents-api-openapi.yml
  - type: Authentication
    url: authentication/fixie-authentication.yml
  - type: AgenticAccess
    url: agentic-access/fixie-agentic-access.yml
  - type: Conventions
    url: conventions/fixie-conventions.yml
  - type: ErrorCatalog
    url: errors/fixie-problem-types.yml
  - type: Lifecycle
    url: lifecycle/fixie-lifecycle.yml
  - type: DataModel
    url: data-model/fixie-data-model.yml
  - type: Conformance
    url: conformance/fixie-conformance.yml
  - type: AsyncAPI
    url: asyncapi/fixie-webhooks.yml
  - type: Webhooks
    url: asyncapi/fixie-webhooks.yml
- aid: fixie:fixie-api-keys-api
  name: Fixie api_keys API
  description: The api_keys API from Fixie — 2 operation(s) for api_keys.
  humanURL: https://docs.ultravox.ai/
  baseURL: https://api.ultravox.ai/api
  tags:
  - api_keys
  properties:
  - type: OpenAPI
    url: openapi/fixie-api-keys-api-openapi.yml
  - type: Authentication
    url: authentication/fixie-authentication.yml
  - type: AgenticAccess
    url: agentic-access/fixie-agentic-access.yml
  - type: Conventions
    url: conventions/fixie-conventions.yml
  - type: ErrorCatalog
    url: errors/fixie-problem-types.yml
  - type: Lifecycle
    url: lifecycle/fixie-lifecycle.yml
  - type: DataModel
    url: data-model/fixie-data-model.yml
  - type: Conformance
    url: conformance/fixie-conformance.yml
  - type: AsyncAPI
    url: asyncapi/fixie-webhooks.yml
  - type: Webhooks
    url: asyncapi/fixie-webhooks.yml
- aid: fixie:fixie-call-throttles-api
  name: Fixie call_throttles API
  description: The call_throttles API from Fixie — 2 operation(s) for call_throttles.
  humanURL: https://docs.ultravox.ai/
  baseURL: https://api.ultravox.ai/api
  tags:
  - call_throttles
  properties:
  - type: OpenAPI
    url: openapi/fixie-call-throttles-api-openapi.yml
  - type: Authentication
    url: authentication/fixie-authentication.yml
  - type: AgenticAccess
    url: agentic-access/fixie-agentic-access.yml
  - type: Conventions
    url: conventions/fixie-conventions.yml
  - type: ErrorCatalog
    url: errors/fixie-problem-types.yml
  - type: Lifecycle
    url: lifecycle/fixie-lifecycle.yml
  - type: DataModel
    url: data-model/fixie-data-model.yml
  - type: Conformance
    url: conformance/fixie-conformance.yml
  - type: AsyncAPI
    url: asyncapi/fixie-webhooks.yml
  - type: Webhooks
    url: asyncapi/fixie-webhooks.yml
- aid: fixie:fixie-calls-api
  name: Fixie calls API
  description: The calls API from Fixie — 13 operation(s) for calls.
  humanURL: https://docs.ultravox.ai/
  baseURL: https://api.ultravox.ai/api
  tags:
  - calls
  properties:
  - type: OpenAPI
    url: openapi/fixie-calls-api-openapi.yml
  - type: Authentication
    url: authentication/fixie-authentication.yml
  - type: AgenticAccess
    url: agentic-access/fixie-agentic-access.yml
  - type: Conventions
    url: conventions/fixie-conventions.yml
  - type: ErrorCatalog
    url: errors/fixie-problem-types.yml
  - type: Lifecycle
    url: lifecycle/fixie-lifecycle.yml
  - type: DataModel
    url: data-model/fixie-data-model.yml
  - type: Conformance
    url: conformance/fixie-conformance.yml
  - type: AsyncAPI
    url: asyncapi/fixie-webhooks.yml
  - type: Webhooks
    url: asyncapi/fixie-webhooks.yml
- aid: fixie:fixie-corpora-api
  name: Fixie corpora API
  description: The corpora API from Fixie — 8 operation(s) for corpora.
  humanURL: https://docs.ultravox.ai/
  baseURL: https://api.ultravox.ai/api
  tags:
  - corpora
  properties:
  - type: OpenAPI
    url: openapi/fixie-corpora-api-openapi.yml
  - type: Authentication
    url: authentication/fixie-authentication.yml
  - type: AgenticAccess
    url: agentic-access/fixie-agentic-access.yml
  - type: Conventions
    url: conventions/fixie-conventions.yml
  - type: ErrorCatalog
    url: errors/fixie-problem-types.yml
  - type: Lifecycle
    url: lifecycle/fixie-lifecycle.yml
  - type: DataModel
    url: data-model/fixie-data-model.yml
  - type: Conformance
    url: conformance/fixie-conformance.yml
  - type: AsyncAPI
    url: asyncapi/fixie-webhooks.yml
  - type: Webhooks
    url: asyncapi/fixie-webhooks.yml
- aid: fixie:fixie-deleted-calls-api
  name: Fixie deleted_calls API
  description: The deleted_calls API from Fixie — 2 operation(s) for deleted_calls.
  humanURL: https://docs.ultravox.ai/
  baseURL: https://api.ultravox.ai/api
  tags:
  - deleted_calls
  properties:
  - type: OpenAPI
    url: openapi/fixie-deleted-calls-api-openapi.yml
  - type: Authentication
    url: authentication/fixie-authentication.yml
  - type: AgenticAccess
    url: agentic-access/fixie-agentic-access.yml
  - type: Conventions
    url: conventions/fixie-conventions.yml
  - type: ErrorCatalog
    url: errors/fixie-problem-types.yml
  - type: Lifecycle
    url: lifecycle/fixie-lifecycle.yml
  - type: DataModel
    url: data-model/fixie-data-model.yml
  - type: Conformance
    url: conformance/fixie-conformance.yml
  - type: AsyncAPI
    url: asyncapi/fixie-webhooks.yml
  - type: Webhooks
    url: asyncapi/fixie-webhooks.yml
- aid: fixie:fixie-models-api
  name: Fixie models API
  description: The models API from Fixie — 1 operation(s) for models.
  humanURL: https://docs.ultravox.ai/
  baseURL: https://api.ultravox.ai/api
  tags:
  - models
  properties:
  - type: OpenAPI
    url: openapi/fixie-models-api-openapi.yml
  - type: Authentication
    url: authentication/fixie-authentication.yml
  - type: AgenticAccess
    url: agentic-access/fixie-agentic-access.yml
  - type: Conventions
    url: conventions/fixie-conventions.yml
  - type: ErrorCatalog
    url: errors/fixie-problem-types.yml
  - type: Lifecycle
    url: lifecycle/fixie-lifecycle.yml
  - type: DataModel
    url: data-model/fixie-data-model.yml
  - type: Conformance
    url: conformance/fixie-conformance.yml
  - type: AsyncAPI
    url: asyncapi/fixie-webhooks.yml
  - type: Webhooks
    url: asyncapi/fixie-webhooks.yml
- aid: fixie:fixie-schema-api
  name: Fixie schema API
  description: The schema API from Fixie — 1 operation(s) for schema.
  humanURL: https://docs.ultravox.ai/
  baseURL: https://api.ultravox.ai/api
  tags:
  - schema
  properties:
  - type: OpenAPI
    url: openapi/fixie-schema-api-openapi.yml
  - type: Authentication
    url: authentication/fixie-authentication.yml
  - type: AgenticAccess
    url: agentic-access/fixie-agentic-access.yml
  - type: Conventions
    url: conventions/fixie-conventions.yml
  - type: ErrorCatalog
    url: errors/fixie-problem-types.yml
  - type: Lifecycle
    url: lifecycle/fixie-lifecycle.yml
  - type: DataModel
    url: data-model/fixie-data-model.yml
  - type: Conformance
    url: conformance/fixie-conformance.yml
  - type: AsyncAPI
    url: asyncapi/fixie-webhooks.yml
  - type: Webhooks
    url: asyncapi/fixie-webhooks.yml
- aid: fixie:fixie-sip-api
  name: Fixie sip API
  description: The sip API from Fixie — 3 operation(s) for sip.
  humanURL: https://docs.ultravox.ai/
  baseURL: https://api.ultravox.ai/api
  tags:
  - sip
  properties:
  - type: OpenAPI
    url: openapi/fixie-sip-api-openapi.yml
  - type: Authentication
    url: authentication/fixie-authentication.yml
  - type: AgenticAccess
    url: agentic-access/fixie-agentic-access.yml
  - type: Conventions
    url: conventions/fixie-conventions.yml
  - type: ErrorCatalog
    url: errors/fixie-problem-types.yml
  - type: Lifecycle
    url: lifecycle/fixie-lifecycle.yml
  - type: DataModel
    url: data-model/fixie-data-model.yml
  - type: Conformance
    url: conformance/fixie-conformance.yml
  - type: AsyncAPI
    url: asyncapi/fixie-webhooks.yml
  - type: Webhooks
    url: asyncapi/fixie-webhooks.yml
- aid: fixie:fixie-telephony-configs-api
  name: Fixie telephony_configs API
  description: The telephony_configs API from Fixie — 3 operation(s) for telephony_configs.
  humanURL: https://docs.ultravox.ai/
  baseURL: https://api.ultravox.ai/api
  tags:
  - telephony_configs
  properties:
  - type: OpenAPI
    url: openapi/fixie-telephony-configs-api-openapi.yml
  - type: Authentication
    url: authentication/fixie-authentication.yml
  - type: AgenticAccess
    url: agentic-access/fixie-agentic-access.yml
  - type: Conventions
    url: conventions/fixie-conventions.yml
  - type: ErrorCatalog
    url: errors/fixie-problem-types.yml
  - type: Lifecycle
    url: lifecycle/fixie-lifecycle.yml
  - type: DataModel
    url: data-model/fixie-data-model.yml
  - type: Conformance
    url: conformance/fixie-conformance.yml
  - type: AsyncAPI
    url: asyncapi/fixie-webhooks.yml
  - type: Webhooks
    url: asyncapi/fixie-webhooks.yml
- aid: fixie:fixie-tools-api
  name: Fixie tools API
  description: The tools API from Fixie — 4 operation(s) for tools.
  humanURL: https://docs.ultravox.ai/
  baseURL: https://api.ultravox.ai/api
  tags:
  - tools
  properties:
  - type: OpenAPI
    url: openapi/fixie-tools-api-openapi.yml
  - type: Authentication
    url: authentication/fixie-authentication.yml
  - type: AgenticAccess
    url: agentic-access/fixie-agentic-access.yml
  - type: Conventions
    url: conventions/fixie-conventions.yml
  - type: ErrorCatalog
    url: errors/fixie-problem-types.yml
  - type: Lifecycle
    url: lifecycle/fixie-lifecycle.yml
  - type: DataModel
    url: data-model/fixie-data-model.yml
  - type: Conformance
    url: conformance/fixie-conformance.yml
  - type: AsyncAPI
    url: asyncapi/fixie-webhooks.yml
  - type: Webhooks
    url: asyncapi/fixie-webhooks.yml
- aid: fixie:fixie-voices-api
  name: Fixie voices API
  description: The voices API from Fixie — 4 operation(s) for voices.
  humanURL: https://docs.ultravox.ai/
  baseURL: https://api.ultravox.ai/api
  tags:
  - voices
  properties:
  - type: OpenAPI
    url: openapi/fixie-voices-api-openapi.yml
  - type: Authentication
    url: authentication/fixie-authentication.yml
  - type: AgenticAccess
    url: agentic-access/fixie-agentic-access.yml
  - type: Conventions
    url: conventions/fixie-conventions.yml
  - type: ErrorCatalog
    url: errors/fixie-problem-types.yml
  - type: Lifecycle
    url: lifecycle/fixie-lifecycle.yml
  - type: DataModel
    url: data-model/fixie-data-model.yml
  - type: Conformance
    url: conformance/fixie-conformance.yml
  - type: AsyncAPI
    url: asyncapi/fixie-webhooks.yml
  - type: Webhooks
    url: asyncapi/fixie-webhooks.yml
- aid: fixie:fixie-webhooks-api
  name: Fixie webhooks API
  description: The webhooks API from Fixie — 2 operation(s) for webhooks.
  humanURL: https://docs.ultravox.ai/
  baseURL: https://api.ultravox.ai/api
  tags:
  - webhooks
  properties:
  - type: OpenAPI
    url: openapi/fixie-webhooks-api-openapi.yml
  - type: Authentication
    url: authentication/fixie-authentication.yml
  - type: AgenticAccess
    url: agentic-access/fixie-agentic-access.yml
  - type: Conventions
    url: conventions/fixie-conventions.yml
  - type: ErrorCatalog
    url: errors/fixie-problem-types.yml
  - type: Lifecycle
    url: lifecycle/fixie-lifecycle.yml
  - type: DataModel
    url: data-model/fixie-data-model.yml
  - type: Conformance
    url: conformance/fixie-conformance.yml
  - type: AsyncAPI
    url: asyncapi/fixie-webhooks.yml
  - type: Webhooks
    url: asyncapi/fixie-webhooks.yml
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: DomainSecurity
  url: security/fixie-domain-security.yml
- type: TrustCenter
  url: security/fixie-trust-center.yml
- type: Packages
  url: packages/fixie-packages.yml
- type: SDKs
  url: packages/fixie-packages.yml
- type: ChangeLog
  url: changelog/fixie-changelog.yml
- type: AgentSkill
  url: skills/_index.yml
- type: LLMsTxt
  url: llms/fixie-llms.txt
- type: StatusPage
  url: https://status.ultravox.ai
- type: Deprecation
  url: https://docs.ultravox.ai/changelog/deprecation
- type: Webhooks
  url: asyncapi/fixie-webhooks.yml
- type: DeveloperPortal
  url: https://docs.ultravox.ai/
- type: Documentation
  url: https://docs.ultravox.ai/
- type: APIReference
  url: https://docs.ultravox.ai/api-reference
- type: GettingStarted
  url: https://docs.ultravox.ai/gettingstarted/quickstart/agent-console
- type: GitHubOrganization
  url: https://github.com/fixie-ai
- type: Blog
  url: https://ultravox.ai/blog
- type: Pricing
  url: https://ultravox.ai/pricing
- type: SignUp
  url: https://app.ultravox.ai
- type: Login
  url: https://app.ultravox.ai
- type: TermsOfService
  url: https://ultravox.ai/terms
- type: PrivacyPolicy
  url: https://ultravox.ai/privacy
- type: Support
  url: mailto:hello@ultravox.ai
- type: Website
  url: https://ultravox.ai/
x-enrichment:
  date: '2026-07-19'
  status: backfilled
  pass: local-v1
  note: backfilled from .gitignore signal + verified work evidence