Redcast MCP servers
Give AI Chat tools from Model Context Protocol servers, remote or running on your Mac.
Model Context Protocol servers provide tools a model can call, like reading a folder, searching an issue tracker or looking something up. When you add a server, AI Chat gives its tools to the model during your conversations.
Turn it on in Settings → AI → MCP Servers → Enable MCP servers. It's off by default, and it only applies while AI Chat is on. While either one is off, Redcast doesn't contact any server or run any server process.
Adding a server
Add MCP Server opens the editor.
| Field | What goes in it |
|---|---|
| Name | Anything. It becomes the server's handle, like @github. |
| Connection | HTTP for a remote server, or Command for one that runs on your Mac. |
| URL | For HTTP. Remote servers must use HTTPS; plain HTTP only works for localhost. |
| Authentication | For HTTP. Header for a fixed credential, or OAuth to sign in through your browser. |
| Header | With Header authentication. A name and value, like Authorization and Bearer …. |
| Client ID / secret | With OAuth. Leave these empty for automatic registration, or enter the credentials your provider gave you. |
| Command | For a local server, like npx. |
| Arguments | Like -y @modelcontextprotocol/server-filesystem ~/Desktop. |
| Environment | NAME=value, one per line, like GITHUB_TOKEN=…. |
| Trust | Ask Each Chat, Always Allow or Never Allow. |
Test Connection connects to the server and reports how many tools it offers, so you find typos here rather than in the middle of a conversation.
Header values, environment values and OAuth credentials are stored in your login Keychain, never in preferences or logs. A full backup includes supported secrets only when you opt into passphrase encryption. Removing a server deletes its stored credentials.
A local server runs with your user account, so only add commands you trust.
Signing in to an OAuth server
Choose HTTP, paste the server's MCP URL, and select OAuth. Click Sign In, complete the provider's sign-in in your browser and review the access it asks for. Return to Redcast when the browser says you can close the tab. Signed in confirms that it worked, and Test Connection checks the signed-in connection and reports how many tools it offers. Save the server to use it in chat.
Leave Client ID and Client secret empty if the provider supports automatic registration. If it
requires you to register your own OAuth client, enter its client ID and secret, if it has one, and
register http://127.0.0.1:4962/callback as the redirect URL. Sign-in times out after five minutes.
If another app is using that port, Redcast tells you so you can close it and try again.
Redcast refreshes tokens automatically before they expire. If a server shows Sign-in required, open it in Settings and sign in again. Sign Out disconnects the server and removes its access and refresh tokens from your Mac. The client registration stays; to fully revoke access, remove the app in the provider's account settings.
Signing in doesn't change the server's trust setting. With Ask Each Chat, Redcast still asks before the first tool call.
Using tools in a chat
The model is offered the tools from every enabled server. When it calls one, a row appears in the reply with a spinner while the tool runs. Consecutive calls share one line, which shows the current call while it runs, then the number of calls and any failures. Click the line to see each call. The reply continues after it, and the calls are saved with the chat.
Talking to one server
Start a message with a handle, like @filesystem list my desktop. A tools icon after your text shows
that the handle was recognized. Only that server's tools are offered, and the handle is removed
before the message is sent. A handle that doesn't match any server is sent as you typed it.
Permission to run
With Ask Each Chat (the default), Redcast asks before the first tool call in each conversation:
- Always Allow remembers your choice for that server.
- Allow This Chat allows calls for this conversation only.
- Don't Allow refuses this one call. esc does the same, and the next call asks again.
Setting a server to Never Allow keeps it in your list without offering its tools. You can only change this in Settings.
A refused or failed call isn't treated as an error. The model is told what happened and can answer without the tool.
Which models get tools
Tools are offered to API connections (OpenAI API, Anthropic Claude, Google Gemini, OpenRouter and OpenAI Compatible endpoints) and to the installed Codex and Claude commands. With those two commands, the command-line tool calls the tools itself. The servers, the confirmation and the rows in the reply work the same as everywhere else, except that OAuth servers you aren't signed in to are left out. Redcast never changes either command's settings.
Your own Codex and Claude MCP servers aren't used in a Redcast chat. Claude is told to use only
Redcast's server list. Codex receives Redcast's servers under their own names, like
tinycast-github, and every server in your Codex configuration is turned off for that chat, so one
of your servers named github is never confused with Redcast's @github. If Redcast can't read
which servers your Codex configuration has, or one of them has a dot or = in its name, Redcast
won't start Codex at all, and the Codex row in Settings explains why.
A few things work differently with Codex:
- Adding, removing or signing in to a server again restarts its helper process, which adds about a
second to your next message. The same happens when you switch between a message that starts with
a handle, like
@github, and one that doesn't, because each offers a different set of servers. - Turning MCP off, or setting a server to Never Allow, removing it or signing out of it, stops the helper right away so the server doesn't keep running. If a reply is in progress at that moment, the helper keeps the server until your next message or until it's been idle for ten minutes.
- An environment variable is only passed to a server that Codex starts if its name uses letters,
digits and
_and doesn't start with a digit.API_TOKENworks, butAPI-TOKENisn't passed on. - Codex can also read content a server publishes, like Notion's guides, without asking. With Codex, Ask Each Chat applies to a server's tools but not to this content. Never Allow still keeps the server out completely.
Apple Intelligence and the installed Grok, OpenCode and Cursor commands never get tools. With those, chat works the same as it does without MCP.
If your organization installs a Claude Code MCP policy, that policy decides MCP for the Claude command, and Redcast doesn't pass any servers to it. The Providers row tells you when this applies.
Limits
- Settings → AI → Chat → Tool call rounds sets how many rounds of tool calls a single reply can use: 25 by default, or 10, 50, 100 or Unlimited. A model that keeps calling tools without answering is stuck, so when it reaches the limit, the reply ends with a note saying how many rounds it used. With Codex, the limit counts individual tool calls instead of rounds, which stops a runaway reply sooner. With Unlimited, a reply only ends when the model finishes, when you click Stop, or, on an API connection, when the tool history passes 1 MB. The reply keeps running while the palette is hidden, and every round is billed by your provider or counted against your plan.
- Each tool result, and the total of all results in one reply, has a size limit.
- Servers start when you use chat and stop after 10 minutes without use, or when Redcast quits. While Codex or Claude is the chat model, a server that runs on your Mac is started by that command instead of by Redcast, so it never runs twice. Its row in Settings shows Stopped until you switch to an API model.
- Redcast doesn't offer anything back to servers. Requests from a server, like sampling, are declined.
Backups
Redcast's full backup can carry MCP server configuration and, separately, encrypted supported secrets. Imported servers arrive off; the preview lists stdio commands before applying them. Review the configuration and enable each server deliberately on the destination Mac.