MCP Concepts

Every AI app re-invents tool connections. MCP — the Model Context Protocol — ends that: one open standard to plug models into tools and data. USB-C for AI.

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What you'll learn

What & why
Host, client, server
Primitives: tools, resources, prompts
Transports & vs function calling

Remember this

MCP = open standard replacing N×M bespoke integrations; servers expose curated capabilities behind a trust boundary
Three roles: host (initiates), client (per-server connection), server (owns capabilities, discovered at connect time)
Primitives: tools (model-invoked actions), resources (app-curated data), prompts (user-selected templates); stdio for local, HTTP for shared

What & why

N apps × M tools = N×M bespoke integrations. MCP = one open protocol (Anthropic, late 2024).
Server = trust boundary: curated tools, credentials stay inside.

Roles

Host: AI app, owns LLM + UX, initiates everything.
Client: one per server, host-owned, carries the protocol.
Server: owns capabilities; announced via discovery at connect.

Primitives

Tools: model-invoked actions (schemas).
Resources: app-curated data (URIs) — model doesn't pull directly.
Prompts: user-selected templates.

Transports & comparison

stdio (local subprocess) vs HTTP (remote/shared, needs auth).
MCP ≠ function calling: protocol AROUND the calls (discovery, lifecycle, composition, ecosystem).

Code: Capability discovery: what a server announces

// What a server exposes at connect time (simplified):
{
  "tools": [
    { "name": "search_tickets",
      "description": "Search support tickets by keyword. Use for customer-history questions; NOT for live account data (use get_account).",
      "inputSchema": { "type": "object",
        "properties": { "query": {"type": "string"}, "limit": {"type": "integer", "default": 5} },
        "required": ["query"] } }
  ],
  "resources": [
    { "uri": "ticket://recent",  "name": "Recent tickets",
      "description": "Last 50 tickets as markdown" },
    { "uri": "kb://article/41",  "name": "Refund policy" }
  ],
  "prompts": [
    { "name": "ticket_summary",
      "description": "Summarize a ticket thread with sentiment" }
  ]
}

// The host turns tools[] into the model's function-calling schema —
// AG-02's description discipline, now riding a standard wire format.