Fastmcp Integration

FastMCP Cloud Integration Skill

This skill provides examples and troubleshooting for FastMCP Cloud integration.

Critical Pattern: Use HTTP Transport

FastMCP Cloud uses HTTP, NOT SSE!

✅ Correct Configuration

Example: Basic FastMCP Cloud Integration

import os
import asyncio
from dotenv import load_dotenv
from claude_agent_sdk import query
from claude_agent_sdk.types import ClaudeAgentOptions

load_dotenv()

ANTHROPIC_API_KEY = os.getenv("ANTHROPIC_API_KEY")
FASTMCP_CLOUD_API_KEY = os.getenv("FASTMCP_CLOUD_API_KEY")

async def main():
    async for message in query(
        prompt="List available tools from the MCP server",
        options=ClaudeAgentOptions(
            model="claude-sonnet-4-20250514",

            # ✅ CRITICAL: Use HTTP for FastMCP Cloud
            mcp_servers={
                "your-server": {
                    "type": "http",  # ← Must be "http" not "sse"
                    "url": "https://your-server.fastmcp.app/mcp",
                    "headers": {
                        "Authorization": f"Bearer {FASTMCP_CLOUD_API_KEY}"
                    }
                }
            },

            # Allow MCP tools
            allowed_tools=["mcp__your-server__*"],

            # Pass API keys via env
            env={
                "ANTHROPIC_API_KEY": ANTHROPIC_API_KEY,
                "FASTMCP_CLOUD_API_KEY": FASTMCP_CLOUD_API_KEY
            }
        )
    ):
        if hasattr(message, 'type') and message.type == 'text':
            print(message.text)

if __name__ == "__main__":
    asyncio.run(main())

Example: Multiple FastMCP Cloud Servers

mcp_servers={
    "cats": {
        "type": "http",
        "url": "https://catsmcp.fastmcp.app/mcp",
        "headers": {"Authorization": f"Bearer {FASTMCP_CLOUD_API_KEY}"}
    },
    "github": {
        "type": "http",
        "url": "https://github-mcp.fastmcp.app/mcp",
        "headers": {"Authorization": f"Bearer {FASTMCP_CLOUD_API_KEY}"}
    }
}

allowed_tools=[
    "mcp__cats__*",      # All CATS tools
    "mcp__github__*",    # All GitHub tools
]

Example: Checking MCP Connection Status

async for message in query(...):
    if hasattr(message, 'type') and message.type == 'system':
        if hasattr(message, 'data') and 'mcp_servers' in message.data:
            for server in message.data['mcp_servers']:
                status = server.get('status', 'unknown')
                name = server.get('name', 'unknown')
                print(f"✅ MCP Server '{name}': {status}")

                if status == 'failed':
                    print("❌ Connection failed!")
                    print("   Check: 1) Using 'type': 'http'")
                    print("   Check: 2) FASTMCP_CLOUD_API_KEY is valid")
                    print("   Check: 3) URL is correct")

❌ Common Mistakes

Wrong transport type:

"type": "sse"  # ❌ Doesn't work with FastMCP Cloud

Missing API key:

# ❌ Not passing FASTMCP_CLOUD_API_KEY
env={"ANTHROPIC_API_KEY": ANTHROPIC_API_KEY}

Wrong package:

from anthropic_agent_sdk import query  # ❌ Wrong!
# Should be:
from claude_agent_sdk import query  # ✅ Correct

Troubleshooting

Symptom: 'mcp_servers': [{'name': 'cats', 'status': 'failed'}]

Causes:

1. Using "type": "sse" instead of "type": "http"
2. Missing or invalid FASTMCP_CLOUD_API_KEY
3. Wrong URL format

Fix:

• Change to "type": "http"
• Verify API key is correct and passed in env parameter
• Ensure URL is https://your-server.fastmcp.app/mcp (with /mcp endpoint)

Symptom: ImportError: No module named 'anthropic_agent_sdk'

Cause: Wrong package name

Fix:

pip uninstall anthropic-agent-sdk  # Remove wrong package
pip install claude-agent-sdk       # Install correct package

Complete Example

See examples/python/fastmcp-cloud-http.py for a full working example.

Environment Variables

Required in .env:

ANTHROPIC_API_KEY=sk-ant-api03-...
FASTMCP_CLOUD_API_KEY=fmcp_...

Must be passed via env parameter:

env={
    "ANTHROPIC_API_KEY": os.getenv("ANTHROPIC_API_KEY"),
    "FASTMCP_CLOUD_API_KEY": os.getenv("FASTMCP_CLOUD_API_KEY")
}

What The Output Actually Looks Like

Example: Successful Connection

When you run your agent, you'll see system messages like this:

# System message with connection status
SystemMessage(
    subtype='init',
    data={
        'type': 'system',
        'session_id': 'c8feee3e-bb62-4dcc-92bc-042b507e614a',
        'mcp_servers': [{'name': 'cats', 'status': 'connected'}],  # ✅ Connected!
        'tools': ['mcp__cats__search_candidates', 'mcp__cats__get_candidate', ...],
        'model': 'claude-sonnet-4-20250514',
        ...
    }
)

What this means:

• 'status': 'connected' ✅ - Your HTTP configuration worked!
• 'tools': [...] - All 163 CATS tools are now available
• Agent can now use mcp__cats__search_candidates, etc.

Example: Failed Connection

If you use wrong transport type, you'll see:

SystemMessage(
    data={
        'mcp_servers': [{'name': 'cats', 'status': 'failed'}],  # ❌ Failed!
        'tools': ['Task', 'Bash', 'Read', ...],  # Only built-in tools, no MCP tools
        ...
    }
)

What this means:

• 'status': 'failed' ❌ - Connection didn't work
• No mcp__cats__* tools available
• Common cause: Using "type": "sse" instead of "type": "http"

Example: Tool Call

When Claude uses an MCP tool:

# Claude decides to call search_candidates
AssistantMessage(
    content=[
        ToolUseBlock(
            id='toolu_01HhvXi5wyvVa2DWtbP8KvJw',
            name='mcp__cats__search_candidates',
            input={'search_string': 'heavy duty mechanic'}
        )
    ]
)

# Tool result comes back
UserMessage(
    content=[
        ToolResultBlock(
            tool_use_id='toolu_01HhvXi5wyvVa2DWtbP8KvJw',
            content='{"count":2,"total":3540,"_embedded":{"candidates":[...]}}'
        )
    ]
)

# Claude responds with analysis
AssistantMessage(
    content=[
        TextBlock(
            text="I found 3,540 heavy duty mechanic candidates. Here are the first 2..."
        )
    ]
)

Real Output From Working Demo

================================================================================
CATS Multi-Tool Agent Demo - Claude Agent SDK
================================================================================

🔌 MCP Server Status:
--------------------------------------------------------------------------------
✅ cats: CONNECTED

📦 Available CATS Tools: 163
   - search_candidates
   - get_candidate
   - list_candidate_custom_fields
   - list_candidate_attachments
   - parse_resume
   ... and 158 more

💬 Claude:
--------------------------------------------------------------------------------
I'll search for heavy duty mechanics using the CATS database...

💬 Claude:
--------------------------------------------------------------------------------
I found 3,540 heavy duty mechanic candidates in the system. Here are the
first 2 results with their Red Seal certification status:

1. **Sahlan Samsuddin**
   - Email: sahlansamsuddin11@gmail.com
   - Location: Mimika, Papua
   - Red Seal Status: Not found in "Notes on Qualifications" field
   - Tags: None

2. **[Next candidate]**
   ...

Additional Examples

See the examples/ directory in this skill:

• examples/multi-server.py - Connecting to multiple FastMCP Cloud servers
• examples/connection-status.py - Testing and troubleshooting connections
• @plugins/claude-agent-sdk/examples/python/complete-example-with-output.py - Full example with output

Related Resources

• Basic example: @plugins/claude-agent-sdk/examples/python/basic-query.py
• FastMCP Cloud example: @plugins/claude-agent-sdk/examples/python/fastmcp-cloud-http.py
• Examples README: @plugins/claude-agent-sdk/examples/README.md
• Agent SDK Docs: @plugins/claude-agent-sdk/docs/sdk-documentation.md
• FastMCP Cloud: https://fastmcp.com
• MCP Protocol: https://modelcontextprotocol.io