fix(mcp): conditionally include body/upload in tool schemas, drop empty body on execution

.changeset/mcp-tool-schema-body-upload.md

@@ -0,0 +1,5 @@
+---
+"@googleworkspace/cli": patch
+---
+
+Fix MCP tool schemas to conditionally include `body`, `upload`, and `page_all` properties only when the underlying Discovery Document method supports them. `body` is included only when a request body is defined, `upload` only when `supportsMediaUpload` is true, and `page_all` only when the method has a `pageToken` parameter. Also drops empty `body: {}` objects that LLMs commonly send on GET methods, preventing 400 errors from Google APIs.

src/mcp_server.rs

@@ -426,27 +426,46 @@ fn walk_resources(prefix: &str, resources: &HashMap<String, RestResource>, tools
                 description = format!("Execute the {} Google API method", tool_name);
             }
 
-            // Generate JSON Schema for MCP input
-            let input_schema = json!({
-                "type": "object",
-                "properties": {
-                    "params": {
-                        "type": "object",
-                        "description": "Query or path parameters (e.g. fileId, q, pageSize)"
-                    },
-                    "body": {
+            // Generate JSON Schema for MCP input — only include body/upload
+            // when the Discovery Document method actually supports them.
+            let mut properties = serde_json::Map::new();
+            properties.insert(
+                "params".to_string(),
+                json!({
+                    "type": "object",
+                    "description": "Query or path parameters (e.g. fileId, q, pageSize)"
+                }),
+            );
+            if method.request.is_some() {
+                properties.insert(
+                    "body".to_string(),
+                    json!({
                         "type": "object",
                         "description": "Request body API object"
-                    },
-                    "upload": {
+                    }),
+                );
+            }
+            if method.supports_media_upload {
+                properties.insert(
+                    "upload".to_string(),
+                    json!({
                         "type": "string",
                         "description": "Local file path to upload as media content"
-                    },
-                    "page_all": {
+                    }),
+                );
+            }
+            if method.parameters.contains_key("pageToken") {
+                properties.insert(
+                    "page_all".to_string(),
+                    json!({
                         "type": "boolean",
                         "description": "Auto-paginate, returning all pages"
-                    }
-                }
+                    }),
+                );
+            }
+            let input_schema = json!({
+                "type": "object",
+                "properties": properties
             });
 
             tools.push(json!({
@@ -756,13 +775,21 @@ async fn execute_mcp_method(
         .transpose()
         .map_err(|e| GwsError::Validation(format!("Failed to serialize params: {e}")))?;
 
-    let body_json_val = arguments.get("body");
+    // Drop empty body objects — LLMs commonly send "body": {} even on GET
+    // methods, which causes Google APIs to return 400.
+    let body_json_val = arguments
+        .get("body")
+        .filter(|v| !v.as_object().is_some_and(|m| m.is_empty()));
     let body_str = body_json_val
         .map(serde_json::to_string)
         .transpose()
         .map_err(|e| GwsError::Validation(format!("Failed to serialize body: {e}")))?;
 
-    let upload_path = if let Some(raw) = arguments.get("upload").and_then(|v| v.as_str()) {
+    let upload_path = if let Some(raw) = arguments
+        .get("upload")
+        .and_then(|v| v.as_str())
+        .filter(|s| !s.is_empty())
+    {
         let p = std::path::Path::new(raw);
         if p.is_absolute() || p.components().any(|c| c == std::path::Component::ParentDir) {
             return Err(GwsError::Validation(format!(