MCP, REST API or webhook: which integration fits?

You want to read data from an app, start an operation or connect two services. The first decision is who starts the workflow: a person in a client, a change in the source app or a recurring schedule? The integration selector turns that choice into a test plan. This is not a ranking of protocols. Several access paths can work together in one integration; each step needs a clear purpose and a result you can verify independently.

Compare the three access paths

MCP describes access to tools, resources and prompts, among other features. A REST API exposes a service’s documented operations through its HTTP interface. A webhook sends data to a receiver when an agreed event occurs. None of these names alone confirms support for your particular task. Read the input schema and check which data is actually returned. The MCP fundamentals guide explains the different types of functionality.

Example: processing a new invoice

Suppose a source app reports a new invoice. A webhook can start processing. If the event contains only an identifier, another step must retrieve the required fields before creating the target record. Write down three expectations for this example: Which identifier arrives? Which fields are read? Which target record should be created? A successful HTTP request does not establish that the amount, currency and account mapping are correct in the destination. Inspect the target record to confirm the outcome.

When a schedule fits the task

A scheduled API request is one possible starting point for a daily inventory reconciliation. Define the time window, time zone and behavior when a previous run is still active. An MCP tool can be part of that workflow, but it does not replace the scheduler. For lists, check every required page. A first page containing twenty results does not prove the inventory is complete. Use documented change filters where available and record the last fully processed position.

Four steps to a verifiable result

1. Choose one test operation with known inputs. Record the source identifier, required fields and expected destination.

2. Check the access path documented by the provider. Do not use an API route as an MCP URL unless it is documented for that purpose.

3. Limit permissions and start with a read test. Use a separate test destination for changes.

4. Repeat the operation and simulate an interrupted run. Check that the destination remains correct and processing can resume.

For implementation, the n8n guide explains the different connection directions. The workflow planner shows documented steps and missing capabilities. Record those gaps in your own test: a missing declaration is not confirmed support. For repeated deliveries, use the webhook checklist to observe acceptance, processing and the final effect separately. Keep the first test small enough to inspect every input and output without guessing.

Does MCP replace a REST API?

Not inherently. An MCP tool may call a REST API internally. The relevant question is which interface the calling client needs.

Is a webhook an MCP server?

No. A webhook URL receives agreed events. That does not imply support for MCP tool calls.

Can MCP start recurring tasks?

Scheduling must be implemented by a client or another service. The protocol alone does not create a scheduler.

Which path should I test first?

Start with an available interface and a small task whose result is known. Then compare permissions, repeated execution and maintenance.

1. MCP architecture
   Show retrieval command

   curl -s https://modelcontextprotocol.io/docs/learn/architecture
2. GitHub REST API practices
   Show retrieval command

   curl -s https://docs.github.com/en/rest/using-the-rest-api/best-practices-for-using-the-rest-api
3. n8n Webhook
   Show retrieval command

   curl -s https://docs.n8n.io/integrations/builtin/core-nodes/n8n-nodes-base.webhook/

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