Fused Engine

Fused is an integration gateway for applications and AI agents. Connect to internal and external services through typed SDKs, a direct API, or MCP servers, with credentials, access policies, retries, and execution records handled by the Engine.

Documentation · Quickstart · Website

How it works

• Registry turns API descriptions into versioned service contracts.
• Engine runs approved operations in your workspace and manages provider credentials.
• CLI configures workspaces, SDKs, and MCP servers through a reviewed plan → apply workflow.

Install and start

You need PostgreSQL 16+ and a Fused license key. Install the Engine and CLI on macOS or Linux:

curl -fsSL https://raw.githubusercontent.com/Usefused/engine/main/install.sh | bash
curl -fsSL https://raw.githubusercontent.com/Usefused/cli/main/install.sh | bash
export PATH="$HOME/.local/bin:$PATH"

Set your database connection, license key, and encryption key, then start the Engine. Generate an encryption key once with openssl rand -base64 32 and keep it for subsequent starts so stored credentials remain readable.

export FUSED_DATABASE_URL='postgres://fused:password@localhost:5432/fused?sslmode=disable'
export FUSED_LICENSE_KEY='<your-license-key>'
export FUSED_ENCRYPTION_KEY='<your-generated-encryption-key>'
fused-engine start

The Engine creates its database tables and starts embedded NATS automatically. Open the Admin UI at localhost:8081; SDK gRPC listens on :50051.

For file-based configuration, see engine.yaml and start with fused-engine start --config /path/to/engine.yaml. Replace its placeholder values and remove the local registry_endpoint to use the default Fused Cloud Registry.

In another terminal, connect the CLI:

fused-cli config set engine-url http://localhost:8081
fused-cli login
fused-cli whoami

See the deployment guide for Docker and hosted Engine setup.

Create an integration interface

With the Engine running, give your application or agent a way to call the services it needs. fused-cli init creates an integration interface exposing the operations you select, while the Engine handles credentials, access policies, and execution.

Choose a typed SDK to call services from your code, an MCP server to make tools available to an AI agent, or a REST API to send HTTP requests without installing a generated package. The examples below use Linear:

Interface	Command	Documentation
Typed SDK	fused-cli init support-sdk --sdk --service linear	SDK quickstart
MCP server	fused-cli init support-mcp --mcp --service linear	MCP server guide
REST API	fused-cli init support-api --api --service linear	REST API guide

Each command guides you through selecting operations and approving setup. Omit the mode flag to choose interactively.

For the callable schema of an exact SDK version, see the per-version OpenAPI export.

Can't find the service you're looking for?

Import its OpenAPI spec, review the plan, then apply it. Replace the example URL with your OpenAPI spec URL:

fused-cli import plan --url https://api.example.com/openapi.yaml --name "Billing API" --slug billing-api
fused-cli import apply
fused-cli init billing-app --sdk --service billing-api

See the API import guide for local file imports and other supported formats.