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Connecting Custom REST APIs

In addition to MCP servers, Hyper allows you to connect to any REST API. This means if a service has an API — whether it’s your own internal API, a third-party service, or any HTTP-based endpoint — you can make it available to your agents as a tool.

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What You’ll Need

Before connecting a custom API, have the following ready:
  • The base URL of the API (e.g., https://api.yourservice.com/v1)
  • Authentication details — API key, bearer token, or other credentials
  • Optionally, an OpenAPI/Swagger specification URL or file for automatic endpoint discovery

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How Custom APIs Work

When you connect a custom API to Hyper:
  1. You provide the API endpoint details and authentication
  2. Hyper registers the API as a callable tool for your agents
  3. When an agent needs to use the API, Hyper handles authentication and makes the request on the agent’s behalf
  4. The response is returned to the agent for processing

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Step-by-Step: Adding a Custom API

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Step 1: Open the Tool Selector

When configuring an agent, open the Tool Selector dialog. You’ll see three tabs at the top: Apps, Custom API, and Custom MCP.

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Step 2: Switch to the Custom API Tab

Click on the Custom API tab. You’ll see an option to add a new API connection.

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Step 3: Click “Add API”

Click the Add API button to open the configuration form.

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Step 4: Configure Your API

1

API Name

Give your API a descriptive name that helps identify what it does. For example: Internal CRM API, Weather Service, or Payment Gateway.
2

Base URL

Enter the base URL for the API. All endpoint paths will be relative to this URL.Example: https://api.example.com/v1
3

Authentication

Configure how to authenticate with the API:
  • API Key — Provide a key that will be sent as a header (e.g., X-API-Key: your-key)
  • Bearer Token — A token sent in the Authorization: Bearer header
  • Custom Headers — Add any custom headers the API requires
  • None — For APIs that don’t require authentication
4

Endpoints (Optional)

If you provide an OpenAPI specification URL, Hyper will automatically discover all available endpoints. Otherwise, you can manually define the endpoints your agent should have access to.

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Step 5: Save and Test

Save the configuration and test the connection to make sure your agent can reach the API successfully.

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Tips & Best Practices

If the API you’re connecting to has an OpenAPI (Swagger) specification, use it. This lets Hyper automatically discover all endpoints, parameters, and response types, making the integration much smoother.
When first connecting a custom API, consider starting with read-only (GET) endpoints. Once you’re confident the integration is working correctly, you can add write operations.
Just like with MCPs, adding descriptive names and notes helps your agents understand when and how to use each API connection effectively.
API keys and tokens are stored securely in Hyper. Never share them in agent instructions or notes. Hyper handles credential injection automatically.

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Custom APIs vs. MCPs — Which Should I Use?

Custom MCPCustom API
Best forServices that offer an MCP endpointAny REST API
SetupJust provide the MCP URL and authProvide base URL, auth, and endpoint config
Tool discoveryAutomatic — MCP servers advertise their toolsAutomatic with OpenAPI spec, or manual
ProtocolModel Context Protocol (structured)HTTP REST
When to chooseThe service has an MCP serverThe service only has a REST API
If a service offers both an MCP endpoint and a REST API, the MCP option is usually easier to set up since tools are discovered automatically.