Can different models use the same MCP server?

Compatible harnesses can share the same MCP server. The harness is the host application containing the MCP client. Here, the model sends tool requests to the harness, which communicates with the Docs server. Access depends on that connection, not just which model you're using.

Model branding doesn't establish access. Your harness needs compatible protocol support and transport, such as local standard input and output or remote Streamable HTTP, valid credentials and permissions, and tools exposed to the model.

Once connected and authorized, the harness asks the Docs server for its tools. The server returns the search_docs schema, describing what the tool does and which inputs it accepts. The harness then exposes that tool in the model's expected format. It may filter available tools or adapt their definitions.

The model proposes a search for refunds. The authorized harness executes it by calling search_docs on the Docs server. In this example, the server returns Refund guide, and the harness passes that result to the model. The harness speaks MCP; the model works through the harness.

A harness supports only local stdio, but the server requires remote HTTP; what must change first?

Use a harness supporting the server's transport. The harness handles the connection, so it needs a compatible transport before any tool call can reach the server. Changing the model or request does not add that connection support.

Identical access doesn't guarantee identical choices. Here, Model A proposes searching for refunds, while Model B proposes return policy, using the same available tool. Neither is necessarily better. The harness must also support each model's tool-use interface, directly or through adaptation.

If connection fails, check client transport support and server configuration. If a tool's missing, check permissions and exposure. If calls are poor, check the model's tool-use support and instructions.

MCP standardizes client-server communication, not model behavior. Compatible, authorized harnesses can share a server, but their policies and the models' tool choices can differ. Check access separately from behavior.