Skip to contents

Register Shiny Inputs and Outputs for MCP Access

Source: R/mcp-wrapper.R
register_io.Rd

Wrap shiny input and output constructors to register metadata so that MCP (Model Context Protocol) agent tools can discover, read, and update them at runtime. When called inside a module loaded by shidashi, the input/output specification is recorded as a side effect and the UI element is returned. When called outside that context (e.g. in a plain Shiny app), the functions fall back to simply evaluating expr.

Usage

register_input(
  expr,
  inputId,
  update,
  description = "",
  writable = TRUE,
  quoted = FALSE,
  env = parent.frame()
)

register_output(
  expr,
  outputId,
  description = "",
  quoted = FALSE,
  env = parent.frame()
)

Arguments

expr

a call expression that creates a shiny input or output widget, e.g. shiny::textInput(inputId = ns("x"), label = "X") or shiny::plotOutput(ns("plot1"), height = "100%").

inputId

character string. The shiny input ID (without the module namespace prefix).

update

character string. The fully qualified update function, e.g. "shiny::updateTextInput". Field mappings such as "shiny::updateSelectInput(value=selected)" override the default argument names passed to the update function.

description

character string. A human-readable description of the input or output purpose, exposed to LLM agents via MCP tools.

writable

logical (default TRUE). Whether the MCP update tool is allowed to change this input.

quoted

logical (default FALSE). If TRUE, expr is treated as already quoted; otherwise it is captured with substitute().

env

the environment in which to evaluate expr.

outputId

character string. The shiny output ID (without the module namespace prefix).

Value

The evaluated UI element produced by expr. The input or output specification is registered as a side effect.

See also

init_app, mcp_wrapper

Examples

if (FALSE) { # \dontrun{
# inside a shidashi module UI function:
ns <- shiny::NS("demo")

register_input(
  expr = shiny::sliderInput(
    inputId = ns("threshold"),
    label = "Threshold",
    min = 0, max = 1, value = 0.5
  ),
  inputId = "threshold",
  update = "shiny::updateSliderInput",
  description = "Filter threshold for the plot"
)

register_output(
  expr = shiny::plotOutput(ns("my_plot"), height = "100%"),
  outputId = "my_plot",
  description = "Scatter plot of filtered data"
)
} # }