Promote _meta arguments on MCP tools

Some MCP servers keep extra settings outside the normal tool arguments. A search tool might advertise only query, while result count, filters, and search type travel in a separate _meta bag the server reads when the tool runs.

Thunk can promote those settings so they look like ordinary arguments. The agent fills them in the same way it fills any other input. When the tool runs, Thunk sends the promoted values the way the MCP server expects.

Use this when a connection's tool is missing an input you know the server supports — especially search and retrieval tools that keep ranking or filter settings out of the advertised schema. Adding a connection is covered in Connections to business applications.

Promote settings on a tool

Open the connection and open the tool you want to change.
Expand Advanced Options. The section starts collapsed.
Paste a JSON Schema object whose properties are the extra settings. For example:

{
  "type": "object",
  "properties": {
    "num_results": {
      "type": "integer",
      "description": "Number of search results to return."
    },
    "query_type": {
      "type": "string",
      "enum": ["ANN", "HYBRID", "FULL_TEXT"],
      "description": "Search algorithm."
    },
    "filters": {
      "type": "object",
      "description": "Filters as a JSON object."
    }
  }
}

Choose Save.

The promoted properties then appear in that tool's parameter list, with the same names, descriptions, and allowed values you put in the schema. The agent sees them there too.

Clear and Save with an empty box removes the overlay for that tool. Properties that already exist on the tool stay as normal arguments — promoting a name the tool already advertises does not move it.

Do not promote protocol keys such as progressToken, or any name that starts with _. Those belong to the MCP protocol, not to your tool.

Environment connections

On an environment MCP connection, promoted values may not reach the server yet. They still appear in the parameter list, and the agent still fills them in, so you do not have to change the schema later.