Raw bytes support sending to mcp server in callTool method

[ghalibansari]

Describe the bug
Unable to send ray bytes / ArrayBuffer / Buffer to mcp server, pydantic validation failes

To Reproduce
Steps to reproduce the behavior:

1. read file from html as buffer send it to client and use callTool method to upload file and it fails

Expected behavior

1. read file from from user in html, using FileReader [ readAsDataURL, readAsArrayBuffer]
2. solution 1 troed : readAsDataURL covert to base64 then Buffer.from(data, 'base64') send to mcp server fails
3. solution 2 tried : readAsDataURL covert to base64 then Buffer.from(data, 'base64') then bytes = new Uint8Array(tmp.buffer, tmp.byteOffset, tmp.byteLength) still fails.
4. readAsArrayBuffer sending this directly still fails and tried few more soultion none worked.

Logs
{
type: "text",
text: 'Error executing tool upload_file_and_email: 1 validation error for upload_file_and_emailArguments files..env\ Input should be a valid bytes [type=bytes_type, input_value={'0': 65, '1': 90, '2': 8....., '333': 109, '334': 34}, input_type=dict] For further information visit https://errors.pydantic.dev/2.11/v/bytes_type`,
}

Additional context

1. at last modified server to hanle base64 directly instead of bytes.
2. i think it call_tool method convert it to stre

[felixweinberger]

Hi @ghalibansari thank you for raising this issue - could you provide some additional details about your setup? You raised this on the typescript-sdk but you're mentioning Pydantic.

Are you using Python as either a server or client here? Do you have any example code to reproduce the issue?

[ghalibansari]

Hey @felixweinberger .
Yes, i have mcp server is in python and mcp client in typescript, was builiding vscode extension for CVS-Health.