diff --git a/.changeset/mcp-hyphen-tool-names.md b/.changeset/mcp-hyphen-tool-names.md
new file mode 100644
index 00000000..edb8a43c
--- /dev/null
+++ b/.changeset/mcp-hyphen-tool-names.md
@@ -0,0 +1,7 @@
+---
+"@googleworkspace/cli": minor
+---
+
+Switch MCP tool names from underscore to hyphen separator (e.g., `drive-files-list` instead of `drive_files_list`). This resolves parsing ambiguity for services/resources with underscores in their names like `admin_reports`. Also fixes the alias mismatch where `tools/list` used Discovery doc names instead of configured service aliases.
+
+**Breaking:** MCP tool names have changed format. Well-behaved clients that discover tools via `tools/list` will pick up new names automatically.
diff --git a/src/mcp_server.rs b/src/mcp_server.rs
index 4fb8e3e6..758f3ac1 100644
--- a/src/mcp_server.rs
+++ b/src/mcp_server.rs
@@ -243,7 +243,7 @@ async fn build_tools_list(config: &ServerConfig) -> Result<Vec<Value>, GwsError>
         let (api_name, version) =
             crate::parse_service_and_version(&[svc_name.to_string()], svc_name)?;
         if let Ok(doc) = crate::discovery::fetch_discovery_document(&api_name, &version).await {
-            walk_resources(&doc.name, &doc.resources, &mut tools);
+            walk_resources(svc_name, &doc.resources, &mut tools);
         } else {
             eprintln!("[gws mcp] Warning: Failed to load discovery document for service '{}'. It will not be available as a tool.", svc_name);
         }
@@ -327,7 +327,7 @@ async fn build_compact_tools_list(config: &ServerConfig) -> Result<Vec<Value>, G
 
     // Add gws_discover meta-tool
     tools.push(json!({
-        "name": "gws_discover",
+        "name": "gws-discover",
         "description": "Query available resources, methods, and parameter schemas for any enabled service. Call with service only to list resources; add resource to list methods; add method to get full parameter schema.",
         "inputSchema": {
             "type": "object",
@@ -359,7 +359,7 @@ async fn build_compact_tools_list(config: &ServerConfig) -> Result<Vec<Value>, G
 
 fn append_workflow_tools(tools: &mut Vec<Value>) {
     tools.push(json!({
-        "name": "workflow_standup_report",
+        "name": "workflow-standup-report",
         "description": "Today's meetings + open tasks as a standup summary",
         "inputSchema": {
             "type": "object",
@@ -369,7 +369,7 @@ fn append_workflow_tools(tools: &mut Vec<Value>) {
         }
     }));
     tools.push(json!({
-        "name": "workflow_meeting_prep",
+        "name": "workflow-meeting-prep",
         "description": "Prepare for your next meeting: agenda, attendees, and linked docs",
         "inputSchema": {
             "type": "object",
@@ -379,7 +379,7 @@ fn append_workflow_tools(tools: &mut Vec<Value>) {
         }
     }));
     tools.push(json!({
-        "name": "workflow_email_to_task",
+        "name": "workflow-email-to-task",
         "description": "Convert a Gmail message into a Google Tasks entry",
         "inputSchema": {
             "type": "object",
@@ -391,7 +391,7 @@ fn append_workflow_tools(tools: &mut Vec<Value>) {
         }
     }));
     tools.push(json!({
-        "name": "workflow_weekly_digest",
+        "name": "workflow-weekly-digest",
         "description": "Weekly summary: this week's meetings + unread email count",
         "inputSchema": {
             "type": "object",
@@ -401,7 +401,7 @@ fn append_workflow_tools(tools: &mut Vec<Value>) {
         }
     }));
     tools.push(json!({
-        "name": "workflow_file_announce",
+        "name": "workflow-file-announce",
         "description": "Announce a Drive file in a Chat space",
         "inputSchema": {
             "type": "object",
@@ -417,10 +417,10 @@ fn append_workflow_tools(tools: &mut Vec<Value>) {
 
 fn walk_resources(prefix: &str, resources: &HashMap<String, RestResource>, tools: &mut Vec<Value>) {
     for (res_name, res) in resources {
-        let new_prefix = format!("{}_{}", prefix, res_name);
+        let new_prefix = format!("{}-{}", prefix, res_name);
 
         for (method_name, method) in &res.methods {
-            let tool_name = format!("{}_{}", new_prefix, method_name);
+            let tool_name = format!("{}-{}", new_prefix, method_name);
             let mut description = method.description.clone().unwrap_or_default();
             if description.is_empty() {
                 description = format!("Execute the {} Google API method", tool_name);
@@ -664,13 +664,13 @@ async fn handle_tools_call(params: &Value, config: &ServerConfig) -> Result<Valu
     let default_args = json!({});
     let arguments = params.get("arguments").unwrap_or(&default_args);
 
-    if tool_name.starts_with("workflow_") {
+    if tool_name.starts_with("workflow-") {
         return Err(GwsError::Other(anyhow::anyhow!(
             "Workflows are not yet fully implemented via MCP"
         )));
     }
 
-    if tool_name == "gws_discover" {
+    if tool_name == "gws-discover" {
         return handle_discover(arguments, config).await;
     }
 
@@ -714,21 +714,31 @@ async fn handle_tools_call(params: &Value, config: &ServerConfig) -> Result<Valu
         return execute_mcp_method(&doc, method, arguments).await;
     }
 
-    // Full mode: tool_name encodes service_resource_method (e.g., drive_files_list)
-    let parts: Vec<&str> = tool_name.split('_').collect();
-    if parts.len() < 3 {
-        return Err(GwsError::Validation(format!(
-            "Invalid API tool name: {}",
+    // Full mode: tool_name encodes service-resource-method (e.g., drive-files-list)
+    // Find the enabled service that is a prefix of the tool name.
+    // This correctly handles hyphenated aliases like "admin-reports".
+    let (svc_alias, rest) = config
+        .services
+        .iter()
+        .filter_map(|s| {
             tool_name
-        )));
-    }
-
-    let svc_alias = parts[0];
+                .strip_prefix(s.as_str())
+                .and_then(|r| r.strip_prefix('-'))
+                .map(|remainder| (s.as_str(), remainder))
+        })
+        .max_by_key(|(s, _)| s.len())
+        .ok_or_else(|| {
+            GwsError::Validation(format!(
+                "Could not determine service from tool name '{}'. No enabled service is a prefix.",
+                tool_name
+            ))
+        })?;
 
-    if !config.services.contains(&svc_alias.to_string()) {
+    let parts: Vec<&str> = rest.split('-').collect();
+    if parts.len() < 2 || parts.iter().any(|p| p.is_empty()) {
         return Err(GwsError::Validation(format!(
-            "Service '{}' is not enabled in this MCP session",
-            svc_alias
+            "Invalid API tool name: '{}'. Expected format: <service>-<resource...>-<method>",
+            tool_name
         )));
     }
 
@@ -739,8 +749,8 @@ async fn handle_tools_call(params: &Value, config: &ServerConfig) -> Result<Valu
     let mut current_resources = &doc.resources;
     let mut current_res = None;
 
-    // Walk: ["drive", "files", "list"] — iterate resource path segments between service and method
-    for res_name in &parts[1..parts.len() - 1] {
+    // Walk resource path segments: everything except the last part (which is the method)
+    for res_name in &parts[..parts.len() - 1] {
         if let Some(res) = current_resources.get(*res_name) {
             current_res = Some(res);
             current_resources = &res.resources;
@@ -1146,7 +1156,7 @@ mod tests {
         let mut tools = Vec::new();
         append_workflow_tools(&mut tools);
         assert_eq!(tools.len(), 5);
-        assert_eq!(tools[0]["name"], "workflow_standup_report");
-        assert_eq!(tools[4]["name"], "workflow_file_announce");
+        assert_eq!(tools[0]["name"], "workflow-standup-report");
+        assert_eq!(tools[4]["name"], "workflow-file-announce");
     }
 }