A tool can finish without raising and still fail to do what it was asked.
Slack answers HTTP 200 with `{"ok": false, "error": "channel_not_found"}`;
an MCP server sets `isError`; a CrewAI AMP action returns
`API request failed: ...`. In every case the call "worked", so the error
text reached the agent as an ordinary result, the agent narrated the
problem in prose, and the run was recorded as a success.
Concretely: five failed `slackbot_send_message` calls each rendered as
"Tool Execution Completed", the task passed, and the crew passed -- with
the only evidence being a sentence in the final answer. Nothing
downstream could tell the difference, and an agent that keeps going on a
step that silently did nothing builds the rest of its work on it.
Give that outcome a type and a reaction:
- `ToolFailure` -- what a tool returns instead of an error string. The
agent still reads prose via `as_agent_message()`, so model behavior is
unchanged; the framework now knows the call failed.
- `ToolFailurePolicy` -- `ignore` (previous behavior), `warn` (default:
record + emit, keep going), `raise` (abort with
`ToolExecutionFailedError`). Resolved most-specific-first: tool, task,
agent, crew.
- `ToolFailureDetectedEvent` -- emitted before a `raise` aborts, so
subscribers always observe the failure. `ToolUsageFinishedEvent` also
carries a `failure` field so a trace UI can mark the call failed
without correlating two events.
- `tool_failures` on `TaskOutput`, `CrewOutput` and `LiteAgentOutput`,
plus `has_tool_failures`, so consumers never parse a string.
Detection is strictly declarative -- no string sniffing, so a tool that
legitimately returns text about an error is never misread as failing.
Failures come from a returned `ToolFailure`, a raised exception, MCP
`isError`, a spent `max_usage_count`, or an unknown tool.
Wired into all four tool-execution paths (the ReAct path and the three
native function-calling implementations). Sources updated to report
structurally: `MCPClient.call_tool_result()` preserves `isError` that
`call_tool()` dropped, and `CrewAIPlatformActionTool` returns a
`ToolFailure` for non-2xx and for caught exceptions.
Two latent bugs fixed along the way: `ToolUsage` assumed every agent has
a `fingerprint` (LiteAgent does not), and policy resolution now tolerates
malformed values rather than letting telemetry take down a tool call.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ETacm2dMASfpMAYUiDu5YG
CrewAI Tools
Empower your CrewAI agents with powerful, customizable tools to elevate their capabilities and tackle sophisticated, real-world tasks.
CrewAI Tools provide the essential functionality to extend your agents, helping you rapidly enhance your automations with reliable, ready-to-use tools or custom-built solutions tailored precisely to your needs.
Quick Links
Homepage | Documentation | Examples | Community
Available Tools
CrewAI provides an extensive collection of powerful tools ready to enhance your agents:
- File Management:
FileReadTool,FileWriteTool - Web Scraping:
ScrapeWebsiteTool,SeleniumScrapingTool - Database Integrations:
MySQLSearchTool - Vector Database Integrations:
MongoDBVectorSearchTool,QdrantVectorSearchTool,WeaviateVectorSearchTool - API Integrations:
SerperApiTool,ExaSearchTool - AI-powered Tools:
DallETool,VisionTool,StagehandTool
And many more robust tools to simplify your agent integrations.
Creating Custom Tools
CrewAI offers two straightforward approaches to creating custom tools:
Subclassing BaseTool
Define your tool by subclassing:
from crewai.tools import BaseTool
class MyCustomTool(BaseTool):
name: str = "Tool Name"
description: str = "Detailed description here."
def _run(self, *args, **kwargs):
# Your tool logic here
Using the tool Decorator
Quickly create lightweight tools using decorators:
from crewai import tool
@tool("Tool Name")
def my_custom_function(input):
# Tool logic here
return output
CrewAI Tools and MCP
CrewAI Tools supports the Model Context Protocol (MCP). It gives you access to thousands of tools from the hundreds of MCP servers out there built by the community.
Before you start using MCP with CrewAI tools, you need to install the mcp extra dependencies:
pip install crewai-tools[mcp]
# or
uv add crewai-tools --extra mcp
To quickly get started with MCP in CrewAI you have 2 options:
Option 1: Fully managed connection
In this scenario we use a contextmanager (with statement) to start and stop the the connection with the MCP server.
This is done in the background and you only get to interact with the CrewAI tools corresponding to the MCP server's tools.
For an STDIO based MCP server:
from mcp import StdioServerParameters
from crewai_tools import MCPServerAdapter
serverparams = StdioServerParameters(
command="uvx",
args=["--quiet", "pubmedmcp@0.1.3"],
env={"UV_PYTHON": "3.12", **os.environ},
)
with MCPServerAdapter(serverparams) as tools:
# tools is now a list of CrewAI Tools matching 1:1 with the MCP server's tools
agent = Agent(..., tools=tools)
task = Task(...)
crew = Crew(..., agents=[agent], tasks=[task])
crew.kickoff(...)
For an SSE based MCP server:
serverparams = {"url": "http://localhost:8000/sse"}
with MCPServerAdapter(serverparams) as tools:
# tools is now a list of CrewAI Tools matching 1:1 with the MCP server's tools
agent = Agent(..., tools=tools)
task = Task(...)
crew = Crew(..., agents=[agent], tasks=[task])
crew.kickoff(...)
Option 2: More control over the MCP connection
If you need more control over the MCP connection, you can instanciate the MCPServerAdapter into an mcp_server_adapter object which can be used to manage the connection with the MCP server and access the available tools.
important: in this case you need to call mcp_server_adapter.stop() to make sure the connection is correctly stopped. We recommend that you use a try ... finally block run to make sure the .stop() is called even in case of errors.
Here is the same example for an STDIO MCP Server:
from mcp import StdioServerParameters
from crewai_tools import MCPServerAdapter
serverparams = StdioServerParameters(
command="uvx",
args=["--quiet", "pubmedmcp@0.1.3"],
env={"UV_PYTHON": "3.12", **os.environ},
)
try:
mcp_server_adapter = MCPServerAdapter(serverparams)
tools = mcp_server_adapter.tools
# tools is now a list of CrewAI Tools matching 1:1 with the MCP server's tools
agent = Agent(..., tools=tools)
task = Task(...)
crew = Crew(..., agents=[agent], tasks=[task])
crew.kickoff(...)
# ** important ** don't forget to stop the connection
finally:
mcp_server_adapter.stop()
And finally the same thing but for an SSE MCP Server:
from mcp import StdioServerParameters
from crewai_tools import MCPServerAdapter
serverparams = {"url": "http://localhost:8000/sse"}
try:
mcp_server_adapter = MCPServerAdapter(serverparams)
tools = mcp_server_adapter.tools
# tools is now a list of CrewAI Tools matching 1:1 with the MCP server's tools
agent = Agent(..., tools=tools)
task = Task(...)
crew = Crew(..., agents=[agent], tasks=[task])
crew.kickoff(...)
# ** important ** don't forget to stop the connection
finally:
mcp_server_adapter.stop()
Considerations & Limitations
Staying Safe with MCP
Always make sure that you trust the MCP Server before using it. Using an STDIO server will execute code on your machine. Using SSE is still not a silver bullet with many injection possible into your application from a malicious MCP server.
Limitations
- At this time we only support tools from MCP Server not other type of primitives like prompts, resources...
- We only return the first text output returned by the MCP Server tool using
.content[0].text
Why Use CrewAI Tools?
- Simplicity & Flexibility: Easy-to-use yet powerful enough for complex workflows.
- Rapid Integration: Seamlessly incorporate external services, APIs, and databases.
- Enterprise Ready: Built for stability, performance, and consistent results.
Contribution Guidelines
We welcome contributions from the community!
- Fork and clone the repository.
- Create a new branch (
git checkout -b feature/my-feature). - Commit your changes (
git commit -m 'Add my feature'). - Push your branch (
git push origin feature/my-feature). - Open a pull request.
Developer Quickstart
pip install crewai[tools]
Development Setup
- Install dependencies:
uv sync - Run tests:
uv run pytest - Run static type checking:
uv run pyright - Set up pre-commit hooks:
pre-commit install
Support and Community
Join our rapidly growing community and receive real-time support:
Build smarter, faster, and more powerful AI solutions—powered by CrewAI Tools.
