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New to agent tools? These 9 concepts unlock the rest. Each card has plain-English context, real syntax examples, and a direct link to ask Claude for help.
Glossary
Agent
AI Agent
An AI program that takes actions, not just chat. You give it a goal and it figures out which tools to use to complete it.
while not done:
thought = llm(goal)
action = tool(thought)
obs = action()
goal = update(goal, obs)
MCP
Model Context Protocol
A standard for how agents talk to tools. Like USB — before it, every tool needed a different cable. MCP is one plug for everything.
{
"mcpServers": {
"github": {
"command": "npx",
"args": ["@github/mcp"]
}
}
}
MCP server
MCP Server
A tool wrapped in the MCP protocol. Plug it in and any agent can use it — zero custom integration code required.
{
"mcpServers": {
"filesystem": {
"command": "npx",
"args": [
"-y",
"@modelcontextprotocol/server-filesystem",
"/Users/you/Documents"
]
}
}
}
API
Application Programming Interface
A structured way for two programs to talk. Your agent sends a request to a URL; the service returns data.
POST api.example.com/messages
{
"text": "Hello from my agent"
}
→ { "id": "msg_123", "status": "sent" }
endpoint
API Endpoint
A specific URL your agent sends requests to. One service can have many endpoints for different actions.
GET /v1/users # list all POST /v1/users # create GET /v1/users/42 # fetch one DELETE /v1/users/42 # remove
auth
Authentication
Proof your agent is allowed to use the tool. Usually an API key in the request header. Store in
.env, never in code.Authorization: Bearer sk-abc123 # .env (add to .gitignore) API_KEY=sk-abc123
.env
Environment Variables
A file holding secrets your code reads at startup. Always in
.gitignore — never commit it.# .env OPENAI_KEY=sk-... SLACK_TOKEN=xoxb-... # .gitignore .env
LLM agnostic
Works with any AI model
Not locked to one provider. Works with Claude, GPT-4, Gemini, or any local model.
# All work: model = "claude-sonnet-4-6" model = "gpt-4o" model = "gemini-2.0-flash"
npx
Node Package Runner
Runs an npm package once without installing it permanently. Almost every MCP server config snippet starts with
npx.npx @modelcontextprotocol/server-filesystem