Clarify MCP server configuration instructions (#59412)

Co-authored-by: Copilot <[email protected]>

Author: belaltaher8

content/copilot/how-tos/use-copilot-agents/coding-agent/extend-coding-agent-with-mcp.md

@@ -50,7 +50,7 @@ Repository administrators can configure MCP servers by following these steps:
 
    Your configuration will be validated to ensure proper syntax.
 
-1. If your MCP server requires a key or secret, add a secret to your {% data variables.product.prodname_copilot_short %} environment. Only secrets with names prefixed with `COPILOT_MCP_` will be available to your MCP configuration. See [Setting up a {% data variables.product.prodname_copilot_short %} environment for {% data variables.copilot.copilot_coding_agent %}](#setting-up-a-copilot-environment-for-copilot-coding-agent).
+1. If your MCP server requires a variable, key, or secret, add a variable or secret to your {% data variables.product.prodname_copilot_short %} environment. Only variables and secrets with names prefixed with `COPILOT_MCP_` will be available to your MCP configuration. See [Setting up a {% data variables.product.prodname_copilot_short %} environment for {% data variables.copilot.copilot_coding_agent %}](#setting-up-a-copilot-environment-for-copilot-coding-agent).
 
 ## Writing a JSON configuration for MCP servers
 
@@ -78,20 +78,23 @@ The configuration object can contain the following keys:
 
 **Required keys for local and remote MCP servers**
 * `tools` (`string[]`): The tools from the MCP server to enable. You may be able to find a list of tools in the server's documentation, or in its code. We strongly recommend that you allowlist specific read-only tools, since the agent will be able to use these tools autonomously and will not ask you for approval first. You can also enable all tools by including `*` in the array.
-* `type` (`string`): {% data variables.copilot.copilot_coding_agent %} accepts `"local"`, `"http"`, or `"sse"`.
+* `type` (`string`): {% data variables.copilot.copilot_coding_agent %} accepts `"local"`, `"stdio"`, `"http"`, or `"sse"`.
 
 **Local MCP specific keys**
 * `command` (`string`): Required. The command to run to start the MCP server.
 * `args` (`string[]`): Required. The arguments to pass to the `command`.
 * `env` (`object`): Optional. The environment variables to pass to the server. This object should map the name of the environment variable that should be exposed to your MCP server to either of the following:
-  * The name of a {% data variables.product.prodname_actions %} secret you have configured, beginning with `COPILOT_MCP_`.
-  * A string value.
+  * The name of a secret you have configured in your {% data variables.product.prodname_copilot_short %} environment, beginning with `COPILOT_MCP_`.
+  * The name of a variable you have configured in your {% data variables.product.prodname_copilot_short %} environment, beginning with `COPILOT_MCP_`.
 
 **Remote MCP specific keys**
 * `url` (`string`): Required. The MCP server's URL.
 * `headers` (`object`): Optional. The headers to attach to requests to the server. This object should map the name of header keys to either of the following:
-  * The name of a {% data variables.product.prodname_actions %} secret you have configured, beginning with `COPILOT_MCP_` preceded by a `$`
-  * A string value
+  * The name of a secret you have configured in your {% data variables.product.prodname_copilot_short %} environment, beginning with `COPILOT_MCP_` preceded by a `$`.
+  * The name of a variable you have configured in your {% data variables.product.prodname_copilot_short %} environment, beginning with `COPILOT_MCP_` preceded by a `$`.
+  * A string value.
+
+Note that all `string` and `string[]` fields besides `tools` & `type` support substitution with a variable or secret you have configured in your {% data variables.product.prodname_copilot_short %} environment, beginning with `COPILOT_MCP_` preceded by a `$`.
 
 ## Example configurations
 
@@ -111,10 +114,12 @@ The [Sentry MCP server](https://github.com/getsentry/sentry-mcp) gives {% data v
       "args": ["@sentry/mcp-server@latest", "--host=$SENTRY_HOST"],
       "tools": ["get_issue_details", "get_issue_summary"],
       "env": {
-        // We can specify an environment variable value as a string...
-        "SENTRY_HOST": "https://contoso.sentry.io",
-        // or refer to a {% data variables.product.prodname_actions %} secret with a name starting with
-        // `COPILOT_MCP_`
+        // We can specify an environment variable value as
+        // a variable in your {% data variables.product.prodname_copilot_short %} environment
+        // where `COPILOT_MCP_SENTRY_HOST` = "https://contoso.sentry.io"...
+        "SENTRY_HOST": "COPILOT_MCP_SENTRY_HOST",
+        // or refer to a secret with a name starting with
+        // `COPILOT_MCP_`.
         "SENTRY_ACCESS_TOKEN": "COPILOT_MCP_SENTRY_ACCESS_TOKEN"
       }
     }