# `cli/unknown-transport` — Unknown MCP transport
- **type**: `https://github.com/zircote/nsip/blob/main/docs/reference/errors/cli/unknown-transport.md`
- **status**: 400 · **exit_code**: 1 · **class**: caller
- **`suggested_fix` applicability**: `machine_applicable`
- **`retry_after`**: never
## When it occurs
The `nsip mcp --transport` value was something other than `stdio` or `http`.
## Recovery
Use `--transport stdio` or `--transport http`.
## Example
```json
{
"type": "https://github.com/zircote/nsip/blob/main/docs/reference/errors/cli/unknown-transport.md",
"title": "Unknown MCP transport",
"status": 400,
"detail": "validation error: unknown transport 'grpc'",
"instance": "urn:nsip:mcp:4e5f6a7b-8c9d-0e1f-2a3b-4c5d6e7f8a9b",
"exit_code": 1,
"suggested_fix": "use --transport stdio or --transport http",
"docs_url": "https://github.com/zircote/nsip/blob/main/docs/reference/errors/cli/unknown-transport.md"
}
```