Agent Capabilities

Overview

CrewAI agents can be extended with five distinct capability types, each serving a different purpose. Understanding when to use each one — and how they work together — is key to building effective agents.

Tools

Callable functions — give agents the ability to take action. Web searches, file operations, API calls, code execution.

MCP Servers

Remote tool servers — connect agents to external tool servers via the Model Context Protocol. Same effect as tools, but hosted externally.

Apps

Platform integrations — connect agents to SaaS apps (Gmail, Slack, Jira, Salesforce) via CrewAI’s platform. Runs locally with a platform integration token.

Skills

Domain expertise — inject instructions, guidelines, and reference material into agent prompts. Skills tell agents how to think.

Knowledge

Retrieved facts — provide agents with data from documents, files, and URLs via semantic search (RAG). Knowledge gives agents what to know.

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The Key Distinction

The most important thing to understand: these capabilities fall into two categories.

Action Capabilities (Tools, MCPs, Apps)

These give agents the ability to do things — call APIs, read files, search the web, send emails. At execution time, all three resolve into the same internal format (BaseTool instances) and appear in a unified tool list the agent can call.

from crewai import Agent
from crewai_tools import SerperDevTool, FileReadTool

agent = Agent(
    role="Researcher",
    goal="Find and compile market data",
    backstory="Expert market analyst",
    tools=[SerperDevTool(), FileReadTool()],  # Local tools
    mcps=["https://mcp.example.com/sse"],     # Remote MCP server tools
    apps=["gmail", "google_sheets"],           # Platform integrations
)

Context Capabilities (Skills, Knowledge)

These modify the agent’s prompt — injecting expertise, instructions, or retrieved data before the agent starts reasoning. They don’t give agents new actions; they shape how agents think and what information they have access to.

from crewai import Agent

agent = Agent(
    role="Security Auditor",
    goal="Audit cloud infrastructure for vulnerabilities",
    backstory="Expert in cloud security with 10 years of experience",
    skills=["./skills/security-audit"],        # Domain instructions
    knowledge_sources=[pdf_source, url_source], # Retrieved facts
)

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When to Use What

You need…	Use	Example
Agent to search the web	Tools	tools=[SerperDevTool()]
Agent to call a remote API via MCP	MCPs	mcps=["https://api.example.com/sse"]
Agent to send emails via Gmail	Apps	apps=["gmail"]
Agent to follow specific procedures	Skills	skills=["./skills/code-review"]
Agent to reference company docs	Knowledge	knowledge_sources=[pdf_source]
Agent to search the web AND follow review guidelines	Tools + Skills	Use both together

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Combining Capabilities

In practice, agents often use multiple capability types together. Here’s a realistic example:

from crewai import Agent
from crewai_tools import SerperDevTool, FileReadTool, CodeInterpreterTool

# A fully-equipped research agent
researcher = Agent(
    role="Senior Research Analyst",
    goal="Produce comprehensive market analysis reports",
    backstory="Expert analyst with deep industry knowledge",

    # ACTION: What the agent can DO
    tools=[
        SerperDevTool(),         # Search the web
        FileReadTool(),          # Read local files
        CodeInterpreterTool(),   # Run Python code for analysis
    ],
    mcps=["https://data-api.example.com/sse"],  # Access remote data API
    apps=["google_sheets"],                      # Write to Google Sheets

    # CONTEXT: What the agent KNOWS
    skills=["./skills/research-methodology"],    # How to conduct research
    knowledge_sources=[company_docs],            # Company-specific data
)

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Comparison Table

Feature	Tools	MCPs	Apps	Skills	Knowledge
Gives agent actions	✅	✅	✅	❌	❌
Modifies prompt	❌	❌	❌	✅	✅
Requires code	Yes	Config only	Config only	Markdown only	Config only
Runs locally	Yes	Depends	Yes (with env var)	N/A	Yes
Needs API keys	Per tool	Per server	Integration token	No	Embedder only
Set on Agent	tools=[]	mcps=[]	apps=[]	skills=[]	knowledge_sources=[]
Set on Crew	❌	❌	❌	skills=[]	knowledge_sources=[]

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Deep Dives

Ready to learn more about each capability type?

Tools

Create custom tools, use the 75+ OSS catalog, configure caching and async execution.

MCP Integration

Connect to MCP servers via stdio, SSE, or HTTP. Filter tools, configure auth.

Skills

Build skill packages with SKILL.md, inject domain expertise, use progressive disclosure.

Knowledge

Add knowledge from PDFs, CSVs, URLs, and more. Configure embedders and retrieval.