feat(core): add tools to list and read MCP resources (#25395)

docs/tools/mcp-resources.md

@@ -0,0 +1,44 @@
+# MCP resource tools
+
+MCP resource tools let Gemini CLI discover and retrieve data from contextual
+resources exposed by Model Context Protocol (MCP) servers.
+
+## 1. `list_mcp_resources` (ListMcpResources)
+
+`list_mcp_resources` retrieves a list of all available resources from connected
+MCP servers. This is primarily a discovery tool that helps the model understand
+what external data sources are available for reference.
+
+- **Tool name:** `list_mcp_resources`
+- **Display name:** List MCP Resources
+- **Kind:** `Search`
+- **File:** `list-mcp-resources.ts`
+- **Parameters:**
+  - `serverName` (string, optional): An optional filter to list resources from a
+    specific server.
+- **Behavior:**
+  - Iterates through all connected MCP servers.
+  - Fetches the list of resources each server exposes.
+  - Formats the results into a plain-text list of URIs and descriptions.
+- **Output (`llmContent`):** A formatted list of available resources, including
+  their URI, server name, and optional description.
+- **Confirmation:** No. This is a read-only discovery tool.
+
+## 2. `read_mcp_resource` (ReadMcpResource)
+
+`read_mcp_resource` retrieves the content of a specific resource identified by
+its URI.
+
+- **Tool name:** `read_mcp_resource`
+- **Display name:** Read MCP Resource
+- **Kind:** `Read`
+- **File:** `read-mcp-resource.ts`
+- **Parameters:**
+  - `uri` (string, required): The URI of the MCP resource to read.
+- **Behavior:**
+  - Locates the resource and its associated server by URI.
+  - Calls the server's `resources/read` method.
+  - Processes the response, extracting text or binary data.
+- **Output (`llmContent`):** The content of the resource. For binary data, it
+  returns a placeholder indicating the data type.
+- **Confirmation:** No. This is a read-only retrieval tool.

docs/tools/mcp-server.md

@@ -64,7 +64,8 @@ Gemini CLI supports three MCP transport types:
 
 Some MCP servers expose contextual “resources” in addition to the tools and
 prompts. Gemini CLI discovers these automatically and gives you the possibility
-to reference them in the chat.
+to reference them in the chat. For more information on the tools used to
+interact with these resources, see [MCP resource tools](mcp-resources.md).
 
 ### Discovery and listing