The MCP Gateway specification lacked fields to configure custom entrypoints for backend MCP server containers. This prevented overriding container default entrypoints and passing custom startup arguments.

Changes

Core types (pkg/types/mcp.go, pkg/workflow/tools_types.go)

• Added Entrypoint string field to BaseMCPServerConfig
• Updated mcpServerConfigToMap() to serialize entrypoint field

Parsing & validation

• Extended getMCPConfig() with optional transformContainer parameter to control docker command transformation
• Added entrypoint extraction in tools_parser.go and validation in mcp_config_validation.go

Rendering system (pkg/workflow/mcp-config.go, pkg/workflow/copilot_mcp.go)

• Added PreserveContainerFields flag to MCPConfigRenderer to conditionally preserve container fields
• When MCP Gateway is enabled (shouldGenerateMCPGateway()), container/entrypoint/entrypointArgs are preserved in JSON format for gateway processing
• When gateway is disabled, fields are transformed to docker commands with --entrypoint flag for backward compatibility

Documentation (docs/src/content/docs/reference/mcp-gateway.md)

• Added entrypoint field specification and usage examples

Behavior

Gateway mode (preserves container fields):

tools:
  custom-mcp:
    container: ghcr.io/example/server
    entrypoint: /custom/entrypoint.sh
    entrypointArgs: ["--verbose"]

Generates config for gateway:

{
  "container": "ghcr.io/example/server",
  "entrypoint": "/custom/entrypoint.sh",
  "entrypointArgs": ["--verbose"]
}

Non-gateway mode (transforms to docker command):

{
  "command": "docker",
  "args": ["run", "--rm", "-i", "--entrypoint", "/custom/entrypoint.sh", 
           "ghcr.io/example/server", "--verbose"]
}

• Fixes MCP Gateway spec does not allow container volume mount points to be specified #9388

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