Method API

The plugin augments an Elysia instance with three chainable runtime methods.

mcpTool

app.mcpTool<Input>(
  name: string,
  handler: (input: Input, context: McpInvocationContext) => unknown,
  options?: McpToolOptions
)

Options include title, description, input and output JSON Schema, tool annotations, icons, and custom marshaling limits.

mcpResource

app.mcpResource(
  uriOrTemplate: string,
  handler: (context: McpResourceInvocationContext) => unknown,
  options?: McpResourceOptions
)

A URI containing {variables} becomes a resource template. The handler context includes the requested URI, parsed template variables, the inbound MCP request, optional metadata, and an abort signal when available.

mcpPrompt

app.mcpPrompt<Args extends Record<string, unknown>>(
  name: string,
  handler: (args: Args, context: McpPromptInvocationContext) => unknown,
  options?: McpPromptOptions
)

Prompt options include title, description, argument descriptors, an argument JSON Schema, and icons.

Handler normalization

Tool handlers may return plain values or full McpToolResult objects. Resource handlers may return a plain value, one resource content item, a list, or a full read result. Prompt handlers may return a string, messages, or a complete prompt result.

All public option, registry, invocation, content, result, and JSON-RPC types are exported from the package root.