feat: Add MCP client tool

[mkmeral]

Description

This PR introduces a new MCP (Model Context Protocol) client tool for Strands Agents that provides a high-level interface for connecting to any MCP server with simplified configuration and enhanced functionality.

Key Features:

• Multiple Transport Support: Connect to MCP servers via stdio (for local processes) or SSE (Server-Sent Events) for web-based servers
• Simplified Configuration: Direct parameter passing without complex nested configurations
• Connection Management: Thread-safe connection storage with support for multiple simultaneous connections
• Tool Discovery: List available tools from connected MCP servers
• Direct Tool Invocation: Call MCP tools directly or load them into the agent's tool registry
• Environment Variable Support: Pass environment variables to stdio-based MCP servers
• Comprehensive Error Handling: Detailed error messages and connection status tracking

Usage Examples:

# Connect to a custom MCP server
agent.tool.mcp_client(
    action="connect",
    connection_id="my_server",
    transport="stdio",
    command="python",
    args=["server.py"]
)

# List available tools
agent.tool.mcp_client(
    action="list_tools",
    connection_id="my_server"
)

# Call a tool directly
agent.tool.mcp_client(
    action="call_tool",
    connection_id="my_server",
    tool_name="calculate",
    x=10,
    y=20
)

# Load tools into agent's registry for direct access
agent.tool.mcp_client(
    action="load_tools",
    connection_id="my_server"
)

Related Issues

N/A

Documentation PR

N/A - Documentation is included in the README.md update

Type of Change

• Bug fix
• New Tool
• Breaking change
• Other (please describe):

Testing

The implementation includes comprehensive unit tests covering:

• Connection management (stdio and SSE transports)
• Tool listing and discovery
• Direct tool invocation
• Tool loading into agent registry
• Error handling scenarios
• Thread safety
• Full workflow integration tests

Testing commands run:

• hatch fmt --linter ✓
• hatch fmt --formatter ✓
• hatch test --all ✓

Manual Testing

**user:** use perplexity mcp from ~/.aws/amazonq/mcp.json and tell me what techno events are in amsterdam this weekend

**strands:** connected to Perplexity MCP server using `mcp_client(action="connect")` with stdio transport, reading config from ~/.aws/amazonq/mcp.json

**strands:** called `mcp_client(action="call_tool", tool_name="perplexity_ask")` to search for Amsterdam techno events, found 4 events including Amsterdam Sessions at Machinegebouw

**user:** load mcp's tools

**strands:** executed `mcp_client(action="load_tools")` to register MCP tools directly into agent, successfully loaded mcp_perplexity_perplexity_ask tool

**user:** using this tool, tell me what events there are this weekend at radion, lofi and thuishaven

**strands:** directly called loaded `mcp_perplexity_perplexity_ask()` tool without going through mcp_client, found Vault Sessions x BASSIANI event at Radion with full lineup details

Key achievements:

• Connected to MCP server from JSON config file
• Called MCP tools through the client interface
• Loaded MCP tools into agent's native tool registry
• Used loaded MCP tools directly like built-in tools
• Seamless integration of external MCP services into Strands workflow

Checklist

• I have read the CONTRIBUTING document

• I have added tests that prove my fix is effective or my feature works

• I have updated the documentation accordingly

• I have added an appropriate example to the documentation to outline the feature

• My changes generate no new warnings

• Any dependent changes have been merged and published

• By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[mkmeral]

Related strands-agents/agent-builder#4

[cagataycali]

Looks great! Approving and leaving a room to team to take a look!

[dbschmigelski]

Approving after offline discussion about consistency, but want to reiterate that mcp_client as the name seems potentially dangerous.