How to Prepare Your Business API for an MCP App
Start with one customer task and the smallest set of API operations needed to complete it. A useful MCP app makes a workflow understandable and safe to operate from an AI conversation. Exposing every endpoint at once usually makes permissions and tool selection harder to review.
Choose a complete task
For a reading tracker, a first workflow could be listing books and updating reading progress. For a task service, it could be finding a task and marking it complete. Write down the expected input, the authoritative server response, and the state the user should see afterward.
A successful HTTP response alone is insufficient if the interface still shows stale data. Check the actual record after the operation and after reopening the host.
Define tools clearly
Give each tool a specific name and a description explaining when it should be used. Define required inputs, permitted values, and useful error responses. Distinguish reads from writes. Return enough information for the host to explain the result without exposing unnecessary customer data.
The MCP tools specification describes the protocol model. Tool descriptions help a host choose an operation; your server must still enforce authorization and validation.
Preserve the customer identity
Map requests to the authenticated customer on the server. Do not accept a caller-supplied account identifier as proof of ownership. Check access to each requested record, and verify that signing out or disconnecting removes the intended access.
Use a disposable record to check creation, reading, updates, and removal. Reopen the app and confirm that the same account sees its own retained records. See security and private data for the broader identity concerns.
Add UI where it improves the task
A list, detail view, or form can make a result easier to inspect. Keep useful text responses too. The MCP Apps overview explains the interactive UI extension. Verify host support and the actual rendered behavior separately in ChatGPT and Claude.
Keep a release boundary
Save the tool definitions and UI together as a versioned release. Review schema compatibility before changing a field that existing records or installed clients use. An update should preserve customer records and existing connections; a rollback should have a clear supported scope.
Kernel Apps is being built around this lifecycle with existing APIs and managed data. Broader access remains through the waitlist. Before inviting users, follow the private app launch checklist.