Agent Capabilities - Crewai

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.

<CardGroup cols={2}> <Card title="Tools" icon="wrench" href="/en/concepts/tools" color="#3B82F6"> **Callable functions** — give agents the ability to take action. Web searches, file operations, API calls, code execution. </Card> <Card title="MCP Servers" icon="plug" href="/en/mcp/overview" color="#8B5CF6"> **Remote tool servers** — connect agents to external tool servers via the Model Context Protocol. Same effect as tools, but hosted externally. </Card> <Card title="Apps" icon="grid-2" color="#EC4899"> **Platform integrations** — connect agents to SaaS apps (Gmail, Slack, Jira, Salesforce) via CrewAI's platform. Runs locally with a platform integration token. </Card> <Card title="Skills" icon="bolt" href="/en/concepts/skills" color="#F59E0B"> **Domain expertise** — inject instructions, guidelines, and reference material into agent prompts. Skills tell agents *how to think*. </Card> <Card title="Knowledge" icon="book" href="/en/concepts/knowledge" color="#10B981"> **Retrieved facts** — provide agents with data from documents, files, and URLs via semantic search (RAG). Knowledge gives agents *what to know*. </Card> </CardGroup>

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.

python

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.

python

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
)

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

Combining Capabilities

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

python

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
)

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=[]`

Deep Dives

Ready to learn more about each capability type?

<CardGroup cols={2}> <Card title="Tools" icon="wrench" href="/en/concepts/tools"> Create custom tools, use the 75+ OSS catalog, configure caching and async execution. </Card> <Card title="MCP Integration" icon="plug" href="/en/mcp/overview"> Connect to MCP servers via stdio, SSE, or HTTP. Filter tools, configure auth. </Card> <Card title="Skills" icon="bolt" href="/en/concepts/skills"> Build skill packages with SKILL.md, inject domain expertise, use progressive disclosure. </Card> <Card title="Knowledge" icon="book" href="/en/concepts/knowledge"> Add knowledge from PDFs, CSVs, URLs, and more. Configure embedders and retrieval. </Card> </CardGroup>