All tools are filtered when using --read-only with AWS MCP Server

[SatoshiMoriyama]

Describe the bug (Security related? please follow https://github.com/aws/mcp-proxy-for-aws/security/policy to report them to AWS Security directly.)

When using the --read-only flag with AWS MCP Server (https://aws-mcp.us-east-1.api.aws/mcp), all tools are filtered out and no tools are available.

I believe this is happening because the AWS MCP Server does not set readOnlyHint=true annotation on any of its tools.

Expected Behavior

When using the --read-only flag, read-only tools should be available. According to the official documentation, the following tools perform read-only operations:

• aws___search_documentation - Search AWS documentation
• aws___read_documentation - Read AWS documentation pages
• aws___recommend - Get content recommendations
• aws___list_regions - List AWS regions
• aws___get_regional_availability - Check regional availability
• aws___suggest_aws_commands - Get AWS API descriptions

Current Behavior

All tools are filtered out with the following log messages:

2026-01-31 06:48:08 | INFO | mcp_proxy_for_aws.middleware.tool_filter | Filtering tools for read only: True
2026-01-31 06:48:08 | INFO | mcp_proxy_for_aws.middleware.tool_filter | Skipping tool aws___call_aws needing write permissions
2026-01-31 06:48:08 | INFO | mcp_proxy_for_aws.middleware.tool_filter | Skipping tool aws___get_regional_availability needing write permissions
2026-01-31 06:48:08 | INFO | mcp_proxy_for_aws.middleware.tool_filter | Skipping tool aws___list_regions needing write permissions
2026-01-31 06:48:08 | INFO | mcp_proxy_for_aws.middleware.tool_filter | Skipping tool aws___read_documentation needing write permissions
2026-01-31 06:48:08 | INFO | mcp_proxy_for_aws.middleware.tool_filter | Skipping tool aws___recommend needing write permissions
2026-01-31 06:48:08 | INFO | mcp_proxy_for_aws.middleware.tool_filter | Skipping tool aws___retrieve_agent_sop needing write permissions
2026-01-31 06:48:08 | INFO | mcp_proxy_for_aws.middleware.tool_filter | Skipping tool aws___search_documentation needing write permissions
2026-01-31 06:48:08 | INFO | mcp_proxy_for_aws.middleware.tool_filter | Skipping tool aws___suggest_aws_commands needing write permissions

Reproduction Steps

1. Configure mcp-proxy-for-aws with --read-only flag:

{
  "mcpServers": {
    "aws-mcp": {
      "command": "uvx",
      "args": [
        "mcp-proxy-for-aws@latest",
        "https://aws-mcp.us-east-1.api.aws/mcp",
        "--service", "aws-mcp",
        "--region", "us-east-1",
        "--profile", "default",
        "--read-only",
        "--log-level", "DEBUG"
      ]
    }
  }
}

2. Connect to the MCP server
3. Check available tools - no tools are available

Possible Solution

Adding readOnlyHint=true annotation to read-only tools would allow the --read-only flag to function correctly.

Additional Information/Context

No response

Operating System

macOS, Kiro IDE

Release Version

v1.1.6

Other information

No response

Search verification

• I have searched existing issues and verified this is not a duplicate

Related issues

None

[mattbrandman]

Hit this same bug