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Call Tool Activity

The Call Tool activity connects to an MCP (Model Context Protocol) server and invokes one of its tools, passing arguments and capturing the tool's response for use in the process. This allows a process to integrate directly with any MCP-compatible server, such as rpa-orch.

Field Description Requirement
Server URL The endpoint URL of the MCP server to connect to. Required
Transport The transport protocol used to communicate with the MCP server (e.g., http). Required
Auth type The authentication method used to connect to the MCP server (e.g., Bearer). Optional
Auth token The authentication token or API key used to connect to the MCP server. Optional
Tool name The name of the MCP tool to invoke on the server. Required
Arguments (JSON) The tool's input arguments, formatted as a JSON string. Optional
Timeout (ms) The maximum duration, in milliseconds, to wait for the tool call to complete. Optional
Result variable name The name of the variable where the tool's response will be stored. Required
Is error variable name The name of a variable that will store whether the tool call resulted in an error. Optional
Raise on tool error? A boolean option to fail the activity if the MCP tool returns an error, instead of only reporting it in Is error variable name. Optional

Action Types & Examples

Tool Invocation

  • Format: string
  • Example Result: list_processes

Arguments

  • Format: JSON string
  • Example Result: {"nameContains": "Invoice", "limit": 10}

Implementation Examples

Field Setup - Server URL: http://dev.robusta.ai:8084/mcp-gateway/mcp/rpc - Transport: http - Auth type: Bearer - Auth token: ${mcpToken} - Tool name: list_processes - Arguments (JSON): {"nameContains": "Invoice", "limit": 10} - Result variable name: mcpResult

Execution Parameters - Timeout (ms): 20000 - Raise on tool error?: true

Technical Notes

When Raise on tool error? is disabled, the activity does not fail on a tool-level error — instead, check Is error variable name after the call to decide how the process should proceed. Enable it to have the activity fail immediately (usable with a Boundary Error Event) when the MCP tool call itself returns an error.