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layout default
title Chapter 3: MCP Elements: Tools, Resources, Prompts, and Schemas
nav_order 3
parent MCP PHP SDK Tutorial

Chapter 3: MCP Elements: Tools, Resources, Prompts, and Schemas

Welcome to Chapter 3: MCP Elements: Tools, Resources, Prompts, and Schemas. In this part of MCP PHP SDK Tutorial: Building MCP Servers in PHP with Discovery and Transport Flexibility, you will build an intuitive mental model first, then move into concrete implementation details and practical production tradeoffs.

This chapter covers primitive design and schema-quality controls in the PHP SDK.

Learning Goals

  • model tools/resources/prompts using PHP attributes or explicit registration
  • control schema generation and validation depth
  • return content in protocol-compliant formats
  • avoid primitive drift that breaks client behavior

Primitive Surface Overview

Primitive Attribute
Tool #[McpTool]
Resource #[McpResource]
Resource Template #[McpResourceTemplate]
Prompt #[McpPrompt]

Schema Discipline Checklist

  1. prefer explicit parameter typing and docblocks for schema quality
  2. use #[Schema] overrides for complex argument contracts
  3. validate error/result content shapes before release
  4. keep names/descriptions stable for client discoverability

Source References

Summary

You now have a schema-first primitive strategy for PHP MCP servers.

Next: Chapter 4: Discovery, Manual Registration, and Caching

Depth Expansion Playbook

Source Code Walkthrough

composer.json

The composer module in composer.json handles a key part of this chapter's functionality:

{
  "name": "mcp/sdk",
  "description": "Model Context Protocol SDK for Client and Server applications in PHP",
  "license": "Apache-2.0",
  "type": "library",
  "authors": [
    {
      "name": "Christopher Hertel",
      "email": "mail@christopher-hertel.de"
    },
    {
      "name": "Kyrian Obikwelu",
      "email": "koshnawaza@gmail.com"
    },
    {
      "name": "Tobias Nyholm",
      "email": "tobias.nyholm@gmail.com"
    }
  ],
  "require": {
    "php": "^8.1",
    "ext-fileinfo": "*",
    "opis/json-schema": "^2.4",
    "php-http/discovery": "^1.20",
    "phpdocumentor/reflection-docblock": "^5.6 || ^6.0",
    "psr/clock": "^1.0",
    "psr/container": "^1.0 || ^2.0",
    "psr/event-dispatcher": "^1.0",
    "psr/http-client": "^1.0",
    "psr/http-factory": "^1.1",
    "psr/http-message": "^1.1 || ^2.0",
    "psr/http-server-handler": "^1.0",
    "psr/http-server-middleware": "^1.0",
    "psr/log": "^1.0 || ^2.0 || ^3.0",
    "symfony/finder": "^5.4 || ^6.4 || ^7.3 || ^8.0",

This module is important because it defines how MCP PHP SDK Tutorial: Building MCP Servers in PHP with Discovery and Transport Flexibility implements the patterns covered in this chapter.

examples/server/oauth-keycloak/keycloak/mcp-realm.json

The mcp-realm module in examples/server/oauth-keycloak/keycloak/mcp-realm.json handles a key part of this chapter's functionality:

{
  "realm": "mcp",
  "enabled": true,
  "registrationAllowed": false,
  "loginWithEmailAllowed": true,
  "duplicateEmailsAllowed": false,
  "resetPasswordAllowed": true,
  "editUsernameAllowed": false,
  "bruteForceProtected": true,
  "accessTokenLifespan": 300,
  "ssoSessionIdleTimeout": 1800,
  "ssoSessionMaxLifespan": 36000,
  "clients": [
    {
      "clientId": "mcp-client",
      "name": "MCP Client Application",
      "description": "Public client for MCP client applications",
      "enabled": true,
      "publicClient": true,
      "standardFlowEnabled": true,
      "directAccessGrantsEnabled": true,
      "serviceAccountsEnabled": false,
      "authorizationServicesEnabled": false,
      "fullScopeAllowed": true,
      "redirectUris": [
        "http://localhost:*",
        "http://127.0.0.1:*"
      ],
      "webOrigins": [
        "http://localhost:*",
        "http://127.0.0.1:*"
      ],
      "defaultClientScopes": [
        "openid",
        "profile",

This module is important because it defines how MCP PHP SDK Tutorial: Building MCP Servers in PHP with Discovery and Transport Flexibility implements the patterns covered in this chapter.

examples/server/oauth-microsoft/docker-compose.yml

The docker-compose module in examples/server/oauth-microsoft/docker-compose.yml handles a key part of this chapter's functionality:

services:
  php:
    build:
      context: .
      dockerfile: Dockerfile
    container_name: mcp-php-microsoft
    volumes:
      - ../../../:/app
    working_dir: /app
    env_file:
      - .env
    environment:
      AZURE_TENANT_ID: ${AZURE_TENANT_ID:-}
      AZURE_CLIENT_ID: ${AZURE_CLIENT_ID:-}
      AZURE_CLIENT_SECRET: ${AZURE_CLIENT_SECRET:-}
    command: >
      sh -c "mkdir -p /app/examples/server/oauth-microsoft/sessions;
      chmod -R 0777 /app/examples/server/oauth-microsoft/sessions;
      touch /app/examples/server/oauth-microsoft/dev.log;
      chmod 0666 /app/examples/server/oauth-microsoft/dev.log;
      touch /app/examples/server/dev.log;
      chmod 0666 /app/examples/server/dev.log;
      composer install --no-interaction --quiet 2>/dev/null || true;
      php-fpm"
    networks:
      - mcp-network

  nginx:
    image: nginx:alpine
    container_name: mcp-nginx-microsoft
    ports:
      - "${MCP_HTTP_PORT:-8000}:80"
    volumes:
      - ./nginx/default.conf:/etc/nginx/conf.d/default.conf:ro
      - ../../../:/app:ro

This module is important because it defines how MCP PHP SDK Tutorial: Building MCP Servers in PHP with Discovery and Transport Flexibility implements the patterns covered in this chapter.

How These Components Connect

flowchart TD
    A[composer]
    B[mcp-realm]
    C[docker-compose]
    A --> B
    B --> C
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