mcp-builder:add-resource

Add MCP Resource

You are helping the user add a resource to their MCP server. Resources provide context that agents can read before calling tools.

What Are Resources?

Resources are data the agent can READ to understand context:

• Database schemas - So the agent knows table structure
• API documentation - So the agent knows available endpoints
• Templates - Pre-built formats for common outputs
• Reference data - Static data the agent might need

When to Use Resources vs Tools

Use Case	Resource or Tool?
Agent needs to read a schema before querying	Resource
Agent needs to fetch live data	Tool
Agent needs reference documentation	Resource
Agent needs to perform an action	Tool

Workflow

Phase 1: Identify the Need

Ask the user:

1. What context does the agent need?
2. Is this data static or dynamic?
3. Will this help the agent make better tool calls?

Phase 2: Design the Resource

Common Resource Types:

Type	URI Pattern	Example
Schema	schema://{name}	schema://database
Template	template://{name}	template://report
Reference	ref://{category}/{name}	ref://api/endpoints
Config	config://{name}	config://settings

Phase 3: Implement the Resource

Python (FastMCP):

# Static resource
@mcp.resource("schema://database")
def get_database_schema() -> str:
    """Database schema for the task management system.
    Read this before querying to understand table structure."""
    return """
    Tables:
    - tasks (id, subject, content_md, status, due_at, assignee_id)
    - users (id, email, name, role)
    - comments (id, task_id, user_id, content, created_at)

    Relationships:
    - tasks.assignee_id -> users.id
    - comments.task_id -> tasks.id
    - comments.user_id -> users.id
    """

# Dynamic resource with template
@mcp.resource("template://task-report")
def get_task_report_template() -> str:
    """Template for generating task status reports."""
    return """
    # Task Report: {title}

    ## Summary
    - Total Tasks: {total}
    - Completed: {completed}
    - In Progress: {in_progress}
    - Pending: {pending}

    ## Details
    {task_list}
    """

TypeScript (MCP SDK):

server.setRequestHandler(ListResourcesRequestSchema, async () => ({
  resources: [
    {
      uri: "schema://database",
      name: "Database Schema",
      description: "Task management database structure",
      mimeType: "text/plain",
    },
  ],
}));

server.setRequestHandler(ReadResourceRequestSchema, async (request) => {
  const { uri } = request.params;

  if (uri === "schema://database") {
    return {
      contents: [{
        uri,
        mimeType: "text/plain",
        text: `Tables:\n- tasks (id, subject, status...)\n- users (id, email...)`,
      }],
    };
  }

  throw new Error(`Unknown resource: ${uri}`);
});

Phase 4: Document the Resource

Add a clear description:

@mcp.resource("schema://database")
def get_database_schema() -> str:
    """Database schema for the task management system.

    Read this resource before:
    - Building database queries
    - Understanding data relationships
    - Validating user input

    The schema includes tables, columns, types, and relationships.
    """

Resource vs Tool: Database Example

Resource (Schema):

@mcp.resource("schema://database")
def get_schema() -> str:
    """Returns the database schema for reference."""
    return "Tables: tasks, users, comments..."

Tool (Query):

@mcp.tool()
def query_database(sql: str) -> str:
    """Execute a read-only SQL query against the database."""
    return db.execute(sql)

Agent Workflow:

1. Agent reads schema://database resource
2. Agent understands table structure
3. Agent constructs appropriate query
4. Agent calls query_database tool

Best Practices

1. Keep resources focused - One resource per concern
2. Use clear URIs - schema://, template://, ref://
3. Document when to read - Help agent know when this resource is useful
4. Keep content concise - Agents have limited context

Update State

After adding the resource, update .mcp-builder/state.json:

{
  "resources": [
    { "uri": "schema://database", "name": "Database Schema" }
  ]
}