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.
Real signal across most facets with visible, nameable gaps — the contract exists but is thin, or the portal is good while governance and commercial terms are absent.
API Evangelist profiles Fixie the way a machine reads it — 19 machine-readable artifacts across 14 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 — Fixie scores 51.7/100 (developing), with a separate agent-readiness read of 42/100 (agent aware). 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
How this is scored →scored 2026-07-27 · rubric v0.5
How we profile Fixie
Each block below is one kind of artifact we hold for Fixie. 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 14
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.
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 within the panel for all 14 ·
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.
Fixie Webhooks
ASYNCAPISecurity 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 Fixie — 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 4
Portal, sign-up, and the first successful call
Documentation 2
Reference material describing how the API behaves
Agent Surfaces 2
MCP servers, agent skills, and machine-readable catalogs
Design & Contract 1
Pagination, idempotency, versioning, errors, and events
Build 3
SDKs, sample code, and the tooling you integrate with
Access & Security 2
Authentication, authorization, and security posture
Operate 4
Status, limits, changes, and where to get help
Commercial 3
Pricing, plans, and the legal terms of use
Company 2
The organization behind the API
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