Authentication

Create an API key in your Fusara profile. Existing Fusara integration keys work with v3. You do not need a separate API account or wallet.

Use the Authorization header on server-to-server requests:

Authorization: Bearer YOUR_API_KEY

If your HTTP client requires a named API-key header, use this alternative:

X-API-Key: YOUR_API_KEY

Send one of these headers, never both. Do not put keys in query strings. Signing in to the Fusara website does not authenticate a request to /api/v3; browser cookies are not API credentials.

Reading your balance verifies the key without starting a generation:

curl 'https://fusara.ai/api/v3/balance' \
  -H "Authorization: Bearer $FUSARA_API_KEY"

200 confirms that the request was authorized. A zero balance is a valid response. Creating a generation still requires sufficient available funds and access to the selected model.

Operation	API key
Read published models and their schemas	Not required
Estimate using model settings and text	Not required
Estimate with media, references or LoRAs	Required
Generate, read runs, list history or cancel	Required
Read balance or import media	Required

An optional key adds resource choices accessible to your account when discovering models. If you supply a key, it must be valid, even on an otherwise public endpoint.

OpenAPI at /api/v3/openapi.json, these guides and the model playground are public. Reading them does not require a key.

Store the key in an environment variable or your secret manager. Call Fusara from your backend; do not embed a key in a public browser bundle, mobile application, shared URL or copied example.

The examples read FUSARA_API_KEY from the environment. They do not require you to paste a key into this documentation.

Manage keys from your profile. When replacing a key, update the applications that use it before revoking the old one. Revoked credentials can no longer authenticate new requests.

Run ownership belongs to the user behind the key. A replacement key for that same user can still read their retained v3 runs; rotation does not create a new history. Sharing a company balance does not grant access to another user's runs.

• 401: check that the key is present, current and sent with the correct header. Remove accidental whitespace or copied quotation marks.
• 400 with conflicting credentials: send only one supported authentication header.
• A resource returns 404: confirm that it belongs to the user behind this key. Inaccessible resources are not exposed through a separate lookup.

For assistance, retain the response's X-Request-Id header. Do not include your API key in a support message. More error guidance.

MCP can use an API key or a supported account OAuth connection. See MCP setup for the actual endpoint and connection options.