Tool Forwarding

Setup (both are required)

Tool forwarding needs both an IAM grant and a service setting — IAM access does not override the service setting.

1. Enable the service action: turn on FORWARD_MCP_TOOLS in the stack’s agent action configuration (API or console).

2. IAM: grant agentaccess-mcp:CallForwardedTool (plus agentaccess-mcp:InvokeMcp to establish the session, and any computer-use actions the agent also uses), scoped to the stack with the agentaccess-mcp:StackArn condition key. Prefer enumerated actions over agentaccess-mcp:*:

   jsonCopy

   {
     "Effect": "Allow",
     "Action": [
       "agentaccess-mcp:InvokeMcp",
       "agentaccess-mcp:CallForwardedTool"
     ],
     "Resource": "*",
     "Condition": {
       "ArnLike": { "agentaccess-mcp:StackArn": "arn:aws:appstream:<region>:<account>:stack/<stack>" }
     }
   }

3. Manifest on the fleet image at C:/ProgramData/NICE/dcv/mcp_server_redirection_config.json:

   jsonCopy

   {
     "mcpServers": {
       "filesystem": {
         "command": "C:/path/to/python.exe",
         "args": ["C:/mcpServerPath/filesystem.py", "C:/Users/Public/Documents"]
       },
       "weather": {
         "command": "C:/Program Files/my-mcp/weather.exe"
       }
     }
   }

   Only command (required, absolute path) and args (optional) are supported — no env vars or working directory. Servers inherit the session environment and run as the session user. The manifest must be saved as UTF-8 without a BOM — the service rejects a manifest that has one (Windows PowerShell 5.1’s writes a BOM; ensure your editor/tool saves plain UTF-8).

Constraints

• stdio transport only. Each entry launches a process that speaks MCP over stdin/stdout. Remote HTTP/SSE endpoints are not supported — wrap a remote endpoint in a local stdio server if needed.
• Use forward slashes in paths (JSON treats \ as an escape). Windows accepts / in absolute paths.
• 5-second tool-call timeout. Each forwarded tool call must complete within 5s or the server cancels it and returns an error. Design forwarded tools to return quickly.

How forwarded tools appear

Forwarded tools are renamed to avoid collisions:

e.g. a get_forecast tool on the weather server appears as forwarded___weather___get_forecast. Agent code matching on tool names must expect this prefix. (Note: Bedrock Converse requires tool names match [a-zA-Z0-9_-]+, so some clients normalize dots to dashes — match forwarded tools by description, not exact spelling.)

Requirements

Fleet image with a DCV Server build that supports MCP forwarding (check the current Agent Access documentation (opens in a new tab) for the minimum version), Desktop stream view, FORWARD_MCP_TOOLS enabled on the stack, and MCP server binaries installed system-wide on the image.