OpenAPI

In Onyx 5.0, OpenAPI actions moved from their own admin page to Admin Panel → Plugins. See Where things moved.

An OpenAPI plugin connects Onyx to a REST API. You give Onyx an OpenAPI schema, and Onyx turns each operation in the schema into a tool. Agents read the operation descriptions and parameters to decide when and how to call the API. OpenAPI plugins work in default Chat and in custom agents. They are not available in Craft. For Craft, use an MCP server or a custom Craft App. Use an OpenAPI plugin for internal services, such as a ticket system or an inventory API, when no MCP server exists.

Add an OpenAPI plugin

Open the OpenAPI form

Go to Admin Panel → Plugins, click Add, then select OpenAPI.

Paste the schema

Paste the schema in OpenAPI Schema Definition. Onyx reads the schema and lists its operations below the field.

The Add OpenAPI plugin form with a schema and the operations that Onyx found

The schema must include:

A servers entry with the base URL of the API.
An operationId for each operation. Onyx uses it as the tool name.
A summary or description for each operation, so the agent knows when to use it.

The Onyx API server must be able to reach the server URL.

Add descriptions

Field	Who reads it
Description for Humans	Users, on the Plugins page and in the agent editor.
Description for Agents	The agent. Explain when to use the API and how to choose operations.

Set default Chat availability

Turn on Enable in default Chat to make the plugin available in chats without a custom agent. Turn it off to make the plugin available only in the custom agents that you add it to.

Configure authentication

Select an authentication method. See Authentication.

Save

Click Add. The plugin shows on the Plugins page with the OpenAPI type.

Authentication

Method	Effect
No authentication	Onyx sends requests without credentials.
Custom Authorization Header	Onyx adds one or more headers that you set, such as `Authorization: Bearer <token>`, to every request. All users share these credentials.
OAuth	Each user signs in with their own account. Onyx sends the user’s access token with each request.
Pass-through	Onyx sends the user’s Onyx sign-in token to the API. This method shows only when Onyx sign-in uses OAuth, OIDC, or Google OAuth.

Custom authorization header

Enter a header name and value. Click the add button to send more than one header.

OAuth

Create an OAuth client in the provider

Set the client’s redirect URI to the Redirect URI that Onyx shows:

https://<your-onyx-domain>/oauth-config/callback

Enter the client details

Enter the Authorization URL, Token URL, OAuth Client ID, and OAuth Client Secret. Optionally, enter Scopes as a comma-separated list.

Set PKCE

Turn on PKCE if the provider requires it. Onyx uses the S256 method.

Test the connection

Click Test connection to confirm that Onyx can complete the OAuth flow.

Each user connects their own account from the Plugins page before the agent can call the API for them.

Request placeholders

Use these placeholders anywhere in the schema, for example in the server URL, a path, or a parameter default. Onyx replaces them with the values of the current request at call time.

Placeholder	Value
`CHAT_SESSION_ID`	The ID of the current chat session
`MESSAGE_ID`	The ID of the current message
`USER_ID`	The ID of the current user
`USER_EMAIL`	The email address of the current user

Manage the plugin

Click the plugin on the Plugins page to open its settings.

Tab	Contents
Configuration	Name, descriptions, schema, and Enable in default Chat.
Authentication	The authentication method and credentials.
Tools	The operations that Onyx found in the schema.

The Tools tab with the operations from an OpenAPI schema

The Tools tab is read only. To add, remove, or change an operation, edit the schema in the Configuration tab. Turning off Enable in default Chat does not remove the plugin from custom agents. Its credentials and settings stay the same. To remove the plugin from all agents, delete it from the Plugins page.

In Terraform, onyx_custom_tool.enabled sets Enable in default Chat. It does not change custom-agent attachments.

Use the plugin in custom agents

Open the agent editor and select the plugin under Actions. See Agents.

Example

Use this schema to add a plugin that creates and gets agents in Onyx. Replace the server URL with your Onyx API URL.

OpenAPI

{
  "openapi": "3.1.0",
  "info": {
    "title": "Agents API",
    "version": "1.0.0",
    "description": "Minimal OpenAPI schema for creating and fetching agents in Onyx"
  },
  "servers": [
    {
      "url": "https://cloud.onyx.app/api"
    }
  ],
  "paths": {
    "/persona": {
      "post": {
        "summary": "Create Agent (Persona)",
        "operationId": "create_persona",
        "requestBody": {
          "required": true,
          "content": {
            "application/json": {
              "schema": {
                "type": "object",
                "properties": {
                  "name": { "type": "string" },
                  "description": { "type": "string" },
                  "document_set_ids": {
                    "type": "array",
                    "items": { "type": "integer" }
                  },
                  "num_chunks": { "type": "number" },
                  "is_public": { "type": "boolean" },
                  "recency_bias": {
                    "type": "string",
                    "enum": ["favor_recent", "base_decay", "no_decay", "auto"]
                  },
                  "llm_filter_extraction": { "type": "boolean" },
                  "llm_relevance_filter": { "type": "boolean" },
                  "tool_ids": {
                    "type": "array",
                    "items": { "type": "integer" }
                  },
                  "system_prompt": { "type": "string" },
                  "task_prompt": { "type": "string" },
                  "datetime_aware": { "type": "boolean" }
                },
                "required": [
                  "name",
                  "description",
                  "document_set_ids",
                  "num_chunks",
                  "is_public",
                  "recency_bias",
                  "llm_filter_extraction",
                  "llm_relevance_filter",
                  "tool_ids",
                  "system_prompt",
                  "task_prompt",
                  "datetime_aware"
                ]
              }
            }
          }
        },
        "responses": {
          "200": { "description": "Created" }
        }
      }
    },
    "/persona/{persona_id}": {
      "get": {
        "summary": "Get Agent (Persona) By ID",
        "operationId": "get_persona",
        "parameters": [
          {
            "name": "persona_id",
            "in": "path",
            "required": true,
            "schema": { "type": "integer" }
          }
        ],
        "responses": {
          "200": { "description": "OK" }
        }
      }
    }
  }
}

Getting Started

Language Models

Connectors

Managing Features

Access Control

Advanced Configs

Auditing

Plans & Billing

Miscellaneous

Add an OpenAPI plugin

Authentication

Custom authorization header

OAuth

Request placeholders

Manage the plugin

Use the plugin in custom agents

Example

​Add an OpenAPI plugin

​Authentication

​Custom authorization header

​OAuth

​Request placeholders

​Manage the plugin

​Use the plugin in custom agents

​Example

Add an OpenAPI plugin

Authentication

Custom authorization header

OAuth

Request placeholders

Manage the plugin

Use the plugin in custom agents

Example