Export Core Types for Third-Party Development

[bunasQ]

Motivation

As the FastMCP framework grows in adoption, third-party developers need access to core types to build their own abstractions and extensions. Currently, many essential types are internal to the framework, making it challenging to create type-safe custom implementations and abstractions like base classes for tools, resources, and prompts.

Benefits

1. Enhanced Developer Experience

   • Better TypeScript support with proper type inference
   • Reduced need to redefine types in third-party code
   • Improved IDE support with accurate type information

2. Safer Third-Party Development

   • Type-safe implementations of custom abstractions
   • Clearer API contract through explicit type exports
   • Reduced potential for runtime errors through compile-time type checking

3. Framework Extensibility

   • Easier creation of reusable base classes and utilities
   • Better support for building custom tool, resource, and prompt abstractions
   • Simplified development of framework plugins and extensions

Example Use Case

import { FastMCP, Context, ToolParameters, ContentResult } from "fastmcp";
import { z } from "zod";

export abstract class BaseTool {
  abstract name: string;
  abstract description: string;
  abstract params: ToolParameters;

  register(server: FastMCP) {
    server.addTool({
      name: this.name,
      description: this.description,
      parameters: this.params,
      execute: this.execute.bind(this),
    });
  }

  abstract execute(
    args: z.infer<typeof this.params>,
    context: Context
  ): Promise<ContentResult>;
}