question on headers for a remote server

[benoitf]

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Discussion Topic

We can declare remote MCP servers like in the example https://github.com/modelcontextprotocol/registry/blob/main/docs/server-json/examples.md#server-with-remote-and-package-options

For remotes, there is a headers field where we can specify an array of Headers with default value, if it's required or not, etc.

I'm facing a question for the GitHub mcp server

for example at https://github.com/github/github-mcp-server?tab=readme-ov-file#install-in-vs-code

it says that we need to provide a Authorization field in the headers

"headers": {
  "Authorization": "Bearer ${input:github_mcp_pat}"
}

my question is the following, how can we say that we want the user to enter the token value and that we can append this value to Bearer <User Token> for the Authorization field.

Because if we declare an Authorization field in the headers, how can we say it requires Bearer prefix. I assume for this kind of field, we don't want to have users being prompted to enter Bearer keyword first

I saw InputWithVariables but it looks like it's for command line arguments, not headers.

[tadasant]

I agree this is a super common auth pattern that we are meant to support, but indeed KeyValueInput already handles this case.

headers takes KeyValueInput:

        "headers": {
          "type": "array",
          "description": "HTTP headers to include",
          "items": {
            "$ref": "#/$defs/KeyValueInput"
          }
        }

KeyValueInput is:

    "KeyValueInput": {
      "allOf": [
        {
          "$ref": "#/$defs/InputWithVariables"
        },
        {
          "type": "object",
          "required": [
            "name"
          ],
          "properties": {
            "name": {
              "type": "string",
              "description": "Name of the header or environment variable.",
              "example": "SOME_VARIABLE"
            }
          }
        }
      ]
    },

InputWithVariables is:

    "InputWithVariables": {
      "allOf": [
        {
          "$ref": "#/$defs/Input"
        },
        {
          "type": "object",
          "properties": {
            "variables": {
              "type": "object",
              "description": "A map of variable names to their values. Keys in the input `value` that are wrapped in `{curly_braces}` will be replaced with the corresponding variable values.",
              "additionalProperties": {
                "$ref": "#/$defs/Input"
              }
            }
          }
        }
      ]
    },

Notably: Keys in the input valuethat are wrapped in{curly_braces} will be replaced with the corresponding variable values.

So the example you're looking for is something like:

  "remotes": [
    {
      "transport_type": "http",
      "url": "https://api.githubcopilot.com/mcp/",
      "headers": [
        {
          "name": "Authorization",
          "value": "Bearer {github_mcp_pat}",
          "variables": {
            "github_mcp_pat": {
              "description": "GitHub Personal Access Token",
              "is_required": true
            }
          }
        }
    }
  ]

Would welcome a PR adding something like this example to the docs in the repo :)

[benoitf]

thanks @tadasant