Package org.apache.juneau.rest.server.mcp

Interface McpToolHandler

public interface McpToolHandler
Handler for a single MCP tool.

Implementations declare a descriptor (returned from tools/list) and a call body invoked when a matching tools/call arrives. Both use the revision-neutral model, so a handler compiles against exactly one protocol revision's worth of assumptions: none.

The BeanStore argument is the per-request bean store, letting handlers look up additional services (or the underlying RestRequest) without this interface depending on REST runtime types.

This is a genuine two-method contract, not a single-method one: both descriptor() and call(Map, BeanStore) are abstract, so it is deliberately not annotated @FunctionalInterface and a bare lambda cannot implement it. Routing calls descriptor() on every registered handler for both tools/list and tools/call, so a handler with no usable descriptor is not a valid handler; making descriptor() abstract catches that at compile time instead of the first request to reach it at runtime. Use of(McpToolSpec, BiFunction) for the common case of wiring both in a single expression.

  • Method Details

    • of

      static McpToolHandler of(McpToolSpec descriptor, BiFunction<Map<String,Object>,BeanStore,McpToolOutcome> call)
      Builds a handler from a fixed descriptor and a call lambda.

      The sanctioned one-expression path for registering a tool: unlike a bare lambda (which cannot satisfy this two-method interface at all), this factory wires both descriptor() and call(Map, BeanStore) from a single call.

      Parameters:
      descriptor - The static descriptor returned from every descriptor() call. Must not be null and must carry a non-blank name (routing matches incoming tools/call requests on name, so a nameless tool would be silently unreachable).
      call - The call body, invoked with the incoming arguments and the per-request bean store. Must not be null.
      Returns:
      A new handler wiring both. Never null.

    • descriptor

      McpToolSpec descriptor()
      Returns the static descriptor for this tool.

      The name value is used by the bound McpRevision to route incoming tools/call requests, so each handler in an McpServerConfig must use a unique name.

      Returns:
      The tool descriptor. Never null.

    • call

      McpToolOutcome call(Map<String,Object> arguments, BeanStore ctx)
      Invokes the tool.
      Parameters:
      arguments - The arguments object passed in the JSON-RPC params (never null; empty map when omitted).
      ctx - Per-request bean store. Never null.
      Returns:
      The call result. Never null.