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Overview

API Reference

Two APIs, one key. The Voice Agents API manages agents, calls, and campaigns. The Models API serves text to speech, speech to text, speech to speech, and the LLM.
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Base URLs

APIBase URLWhat it covers
Voice Agents APIhttps://api.smallest.ai/atoms/v1Agents, versioning, calls, campaigns, audiences, phone numbers, knowledge bases, tools, webhooks, analytics, billing
Models APIhttps://api.smallest.ai/waves/v1Lightning text to speech, Pulse speech to text, Hydra speech to speech, Electron chat completions, voice cloning, pronunciation dictionaries, usage analytics

Both APIs use the same key. Send it as a bearer token on every request:

curl "https://api.smallest.ai/atoms/v1/agent" \
  -H "Authorization: Bearer $SMALLEST_API_KEY"

See Authentication to create a key, and Concurrency and Limits for what a plan allows.

Reading the reference

Every endpoint page shows the request schema, the response schema, and a runnable snippet in cURL, Python, and TypeScript. The Python and TypeScript snippets use the official smallestai packages, so the code you copy matches the SDK method names.

WebSocket endpoints (realtime agent, streaming text to speech, realtime speech to text, Hydra) document the handshake, every message type in both directions, and the close codes.

Errors

Error responses carry an HTTP status and a JSON body with a machine readable error_type or code. The per API error pages list every status and how to recover:

Deprecations

Deprecated endpoints keep working and return a Deprecation: true header. The Deprecations section lists each one with its migration target, and the Agent Versioning migration guide covers the v1 to v2 change endpoint by endpoint.