# StepFun

**Canonical:** https://apis.io/providers/stepfun/  
**Website:** https://www.stepfun.com  
**APIs profiled:** 12

StepFun (阶跃星辰) is a Shanghai-based AI foundation-model company whose open platform serves the Step model family — multimodal reasoning (step-3.7-flash), fast language reasoning (step-3.5-flash), vision, image generation and editing (step-2x-large, step-image-edit-2), and a deep audio stack spanning TTS, voice cloning, ASR, and end-to-end realtime voice (StepAudio 2.5) — via an OpenAI-compatible REST API at api.stepfun.com, an Anthropic-compatible Messages API, WebSocket realtime channels, and a hosted StepSearch MCP server for agent clients.

## Kin Score — 48.2 / 100 (developing)

Scored 2026-08-20 under rubric 0.12.0. Trend: flat (+0.0 from 48.2).

| Facet | Score |
|---|---|
| Discoverability | 81.5 |
| Contract Quality | 44.4 |
| Governance | 18.2 |
| Contract Governance | 18.2 |
| Operational Transparency | 42.1 |
| Developer Ergonomics | 61.9 |
| Commercial Clarity | 44.7 |
| Access Clarity | 44.7 |

## Agent readiness — 41.9 (agent-ready)

| Dimension | Value |
|---|---|
| Spec Presence | yes |
| Agentic Access | no |
| Reversibility Documented | no |
| MCP Server | verified |
| Auth Clarity | yes |
| Idempotency | no |
| Error Semantics | documented |
| OpenAPI Examples | no |
| Rate Limit Signal | documented |
| Event Surface Described | derived |
| Agent Skills | no |
| Well Known Catalog | no |
| Consent Identity | no |
| Agent Card | no |
| Dry Run Mode | no |

## Access

Self-serve signup — onboarding: self-serve, pricing: unknown, trial: no (confidence: medium).

## APIs (12)

- **StepFun Chat Completions API** — OpenAI-compatible chat completions for the Step model family (e.g. step-3.7-flash, step-3.5-flash, stepaudio-2.5-chat), with multimodal image/video/audio message parts, tool cal...
- **StepFun Messages API** — Anthropic Messages API-compatible endpoint (POST /v1/messages) that lets the Anthropic SDK and Claude-style JSON structures run against Step models by pointing base_url at https...
- **StepFun Responses API** — OpenAI Responses API-style endpoint for generating model responses on the StepFun open platform.
- **StepFun Models API** — List available Step models, retrieve a single model, and inspect the model object.
- **StepFun Audio API** — Speech synthesis (TTS), voice cloning with preview, official voice catalog, audio transcription, and file-based / streaming speech recognition (ASR) across the StepAudio 2.5 and...
- **StepFun Realtime API** — Bidirectional realtime voice over WebSocket (wss://api.stepfun.com/v1/realtime) with OpenAI Realtime-style session, conversation, and response events, plus a streaming TTS chann...
- **StepFun Images API** — Image generation, image editing, and image-to-image endpoints for the step-2x-large and step-image-edit-2 models.
- **StepFun Files API** — Upload, list, retrieve, delete files and fetch file content for use with Step models and knowledge bases.
- **StepFun Vector Stores API** — Knowledge-base (vector store) management — create/list/retrieve/delete stores and attach or remove files for retrieval-augmented generation.
- **StepFun Web Search API** — Web search and text-to-image search endpoints (POST /v1/search) billed per call as value-added capabilities.
- **StepFun Token Count API** — Pre-count prompt tokens for a model request (POST /v1/token/count) to estimate usage and cost.
- **StepFun Accounts API** — Retrieve account information including balances (GET /v1/accounts).

## MCP servers (1)

- **StepFun MCP Server** — StepFun operates an official hosted remote MCP server, StepSearch — a search service built on the Model Context Protocol that gives Claude Code, Cline, OpenCode, Goose, and othe...

## Security (2)

- **Stepfun Authentication** — http-bearer-api-key · 1 scheme
- **Stepfun Domain Security** — TLSv1.3 · DNSSEC

## Tags

Artificial Intelligence, LLM, Multi-Modal, Chat Completion, Audio, Speech, Text-to-Speech, Speech Recognition, Image, Real-Time, Vector Stores, China

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/providers/stepfun/). Scores are computed from the provider's own public artifacts under a published rubric.