I think this is an issue with your MCP tool descriptions, it keeps trying to use deprecated properties https://cdn.discordapp.com/attachments/1433840367093940285/1433840369056878672/image.png?ex=693cdda7&is=693b8c27&hm=382d12a0b0e60d78f20dc554fe4da6b89c19c254e0525b362fb76a0cdbea1e0f& https://cdn.discordapp.com/attachments/1433840367093940285/1433840370118299829/image.png?ex=693cdda7&is=693b8c27&hm=ba0b69b622686207edf33b25f5baee72d5deda70d2877f5eee873bcf4f3615ee&

Hey @joelcodes, looks like you are using

SLACK

toolkit, could you try passing

as_user

as true and lmk if it works for you?

I’m not determining this. It’s the AI tool call.

I see, specifying should solve the issue as

Slack

toolkit is supposed to be using tools as a user. Let me check with the team and revert.

Thanks I’ve had to add additional instructions to the LLM to override whatever it’s doing now

Hey @joelcodes, it's a legacy field and it defaults to

false

. You can refere this doc: https://docs.slack.dev/reference/methods/chat.postMessage/ https://cdn.discordapp.com/attachments/1433840367093940285/1437324341179187250/Screenshot_2025-11-10_at_11.41.10.png?ex=6912d41b&is=6911829b&hm=52a8ae2d2ea8b953443dbfc82c32efda76df0a904d455194a23548ff7733a750&

Is there a way to force it not to be used by the MCP server ?

Hey @joelcodes, you need to pass it as

true

or it'll default to

false

resulting in an error. Thanks!

Not sure I’m following. Can you provide an example ?

You can add additional instructions to LLMs(your current solution). For example: "Send a message to <> saying Hi as a user". — Let me know if you face any issues.

This doesn’t work. The Slack MCP is extremely inconsistent due to the instructions its provided about its tools. It seems like it’s been poorly tested

Hey @joelcodes, we are discussing about

as_user

legacy field and will keep you updated.

Thats great news, do we have to redeploy the MCP servers ?

No, you don't need to redeploy your servers. The server will use the updated tool.