MCP and direct APIs are not mutually exclusive. An MCP server can expose tools that call an underlying API. Separate the interface from the model and orchestration: decide whether you need standardized discovery, model reasoning and a particular execution workflow.
What MCP Does Well
MCP standardizes how compatible clients discover and use server capabilities. It can be useful when several applications need the same tools or resources. A conversational host may use a model to select tools, but natural-language interpretation belongs to that host, not to the protocol. The server still needs service integration and authorization.
When a direct API client is sufficient
A direct API client may be the simplest option for a narrow existing workflow. It avoids an additional protocol adapter when no compatible MCP client needs one. That does not make retries, ordering or unattended execution automatic: the client and orchestrator must implement them. MCP-based clients can also support deterministic workflows if designed accordingly.
The Decision Framework
Ask separate questions: Which clients need the interface? Does the task need a model? Who authorizes each operation? What controls ordering, retries and duplicate writes? Unpredictable input can justify interpretation, but it does not force MCP. A scheduled task does not prohibit MCP. Choose the smallest maintainable design that meets the actual requirements.
The Hybrid Architecture
You can share a service layer between an MCP interface and direct clients. Keep source permissions and business rules consistent across both entry points. Separate workloads when throughput, isolation or support needs justify it, rather than imposing a universal split between interactive and automated work. Identify the authoritative record for each field that either path changes.
Cost Comparison
MCP itself does not require a model invocation for every call, so there is no universal token cost per MCP operation. Estimate actual model use, service charges, hosting, connector work and maintenance for each design. Test representative load and failure recovery. A direct API workflow also has operational costs even when the service charges no per-call fee.
Common Mistakes
Avoid choosing a protocol for fashion or rejecting it because a task runs unattended. More serious mistakes include weak authorization, ambiguous tool inputs and unsafe retries that repeat a write. Test denied access and interrupted execution. Keep tool errors distinguishable from a model's explanation so operators can diagnose the failing component.
A practical Google workflow comparison
For a Google workflow, compare an available connector, a direct Google API client and an MCP adapter over a suitable service implementation. Apps Script is an optional runtime with its own identities and quotas. Record the components actually deployed and test them; a generic architecture diagram cannot establish performance, cost or suitability.
Choose by the workflow requirements
Choose the interface and orchestration together, using a bounded workflow and documented acceptance checks. The MCP introduction and Workspace guide below explain the related components. A useful integration proposal names permissions, failure handling, maintenance ownership and estimated workload; its schedule follows that scope rather than a universal deployment promise.