diff --git a/packages/mcp-server/src/features/fetch/index.ts b/packages/mcp-server/src/features/fetch/index.ts
index 628fd79..c3dd1e2 100644
--- a/packages/mcp-server/src/features/fetch/index.ts
+++ b/packages/mcp-server/src/features/fetch/index.ts
@@ -10,17 +10,21 @@ export function registerFetchTool(tools: ToolRegistry, server: Server) {
     type({
       name: '"fetch"',
       arguments: {
-        url: "string",
-        "maxLength?": type("number").describe("Limit response length."),
+        url: type("string").describe("The URL to fetch content from. REQUIRED."),
+        "maxLength?": type("number").describe(
+          "Limit response length. Optional.",
+        ),
         "startIndex?": type("number").describe(
-          "Supports paginated retrieval of content.",
+          "Supports paginated retrieval of content. Optional.",
         ),
         "raw?": type("boolean").describe(
-          "Returns raw HTML content if raw=true.",
+          "Returns raw HTML content if raw=true. Optional.",
         ),
       },
     }).describe(
-      "Reads and returns the content of any web page. Returns the content in Markdown format by default, or can return raw HTML if raw=true parameter is set. Supports pagination through maxLength and startIndex parameters.",
+      "Reads and returns the content of any web page. Returns the content in Markdown format by default, or can return raw HTML if raw=true parameter is set. Supports pagination through maxLength and startIndex parameters. " +
+        "IMPORTANT: The 'url' argument is required. " +
+        "Example: { url: 'https://example.com/page', maxLength: 5000 }",
     ),
     async ({ arguments: args }) => {
       logger.info("Fetching URL", { url: args.url });
diff --git a/packages/mcp-server/src/features/local-rest-api/index.ts b/packages/mcp-server/src/features/local-rest-api/index.ts
index 37a1424..753cf70 100644
--- a/packages/mcp-server/src/features/local-rest-api/index.ts
+++ b/packages/mcp-server/src/features/local-rest-api/index.ts
@@ -25,10 +25,13 @@ export function registerLocalRestApiTools(tools: ToolRegistry, server: Server) {
     type({
       name: '"get_active_file"',
       arguments: {
-        format: type('"markdown" | "json"').optional(),
+        "format?": type('"markdown" | "json"').describe(
+          "Response format: 'markdown' for raw content or 'json' for parsed with frontmatter and tags. Optional, defaults to 'markdown'.",
+        ),
       },
     }).describe(
-      "Returns the content of the currently active file in Obsidian. Can return either markdown content or a JSON representation including parsed tags and frontmatter.",
+      "Returns the content of the currently active file in Obsidian. Can return either markdown content or a JSON representation including parsed tags and frontmatter. " +
+        "Example: { format: 'json' }",
     ),
     async ({ arguments: args }) => {
       const format =
@@ -53,9 +56,15 @@ export function registerLocalRestApiTools(tools: ToolRegistry, server: Server) {
     type({
       name: '"update_active_file"',
       arguments: {
-        content: "string",
+        content: type("string").describe(
+          "The complete new content to write to the file. REQUIRED.",
+        ),
       },
-    }).describe("Update the content of the active file open in Obsidian."),
+    }).describe(
+      "Update the content of the active file open in Obsidian. " +
+        "IMPORTANT: The 'content' argument is required. " +
+        "Example: { content: '# My Note\\n\\nUpdated content here' }",
+    ),
     async ({ arguments: args }) => {
       await makeRequest(LocalRestAPI.ApiNoContentResponse, "/active/", {
         method: "PUT",
@@ -72,9 +81,15 @@ export function registerLocalRestApiTools(tools: ToolRegistry, server: Server) {
     type({
       name: '"append_to_active_file"',
       arguments: {
-        content: "string",
+        content: type("string").describe(
+          "The content to append to the end of the file. REQUIRED.",
+        ),
       },
-    }).describe("Append content to the end of the currently-open note."),
+    }).describe(
+      "Append content to the end of the currently-open note. " +
+        "IMPORTANT: The 'content' argument is required. " +
+        "Example: { content: '\\n\\n## New Section\\n\\nAppended content' }",
+    ),
     async ({ arguments: args }) => {
       await makeRequest(LocalRestAPI.ApiNoContentResponse, "/active/", {
         method: "POST",
@@ -92,7 +107,9 @@ export function registerLocalRestApiTools(tools: ToolRegistry, server: Server) {
       name: '"patch_active_file"',
       arguments: LocalRestAPI.ApiPatchParameters,
     }).describe(
-      "Insert or modify content in the currently-open note relative to a heading, block reference, or frontmatter field.",
+      "Insert or modify content in the currently-open note relative to a heading, block reference, or frontmatter field. " +
+        "IMPORTANT: The 'operation', 'targetType', 'target', and 'content' arguments are required. " +
+        "Example: { operation: 'append', targetType: 'heading', target: 'My Heading', content: '\\n\\nNew content' }",
     ),
     async ({ arguments: args }) => {
       const headers: Record<string, string> = {
@@ -151,11 +168,17 @@ export function registerLocalRestApiTools(tools: ToolRegistry, server: Server) {
     type({
       name: '"show_file_in_obsidian"',
       arguments: {
-        filename: "string",
-        "newLeaf?": "boolean",
+        filename: type("string").describe(
+          "The vault-relative path to the file (e.g., 'notes/my-note.md'). REQUIRED.",
+        ),
+        "newLeaf?": type("boolean").describe(
+          "Whether to open in a new tab. Optional, defaults to false.",
+        ),
       },
     }).describe(
-      "Open a document in the Obsidian UI. Creates a new document if it doesn't exist. Returns a confirmation if the file was opened successfully.",
+      "Open a document in the Obsidian UI. Creates a new document if it doesn't exist. " +
+        "IMPORTANT: The 'filename' argument is required. " +
+        "Example: { filename: 'daily/2025-01-17.md' }",
     ),
     async ({ arguments: args }) => {
       const query = args.newLeaf ? "?newLeaf=true" : "";
@@ -179,11 +202,17 @@ export function registerLocalRestApiTools(tools: ToolRegistry, server: Server) {
     type({
       name: '"search_vault"',
       arguments: {
-        queryType: '"dataview" | "jsonlogic"',
-        query: "string",
+        queryType: type('"dataview" | "jsonlogic"').describe(
+          "The query language to use: 'dataview' for DQL or 'jsonlogic'. REQUIRED.",
+        ),
+        query: type("string").describe(
+          "The search query string in the specified query language. REQUIRED.",
+        ),
       },
     }).describe(
-      "Search for documents matching a specified query using either Dataview DQL or JsonLogic.",
+      "Search for documents matching a specified query using either Dataview DQL or JsonLogic. " +
+        "IMPORTANT: Both 'queryType' and 'query' arguments are required. " +
+        "Example: { queryType: 'dataview', query: 'LIST FROM \"notes\"' }",
     ),
     async ({ arguments: args }) => {
       const contentType =
@@ -212,10 +241,18 @@ export function registerLocalRestApiTools(tools: ToolRegistry, server: Server) {
     type({
       name: '"search_vault_simple"',
       arguments: {
-        query: "string",
-        "contextLength?": "number",
+        query: type("string").describe(
+          "The text search query to find in vault files. REQUIRED.",
+        ),
+        "contextLength?": type("number").describe(
+          "Number of characters of context around matches. Optional.",
+        ),
       },
-    }).describe("Search for documents matching a text query."),
+    }).describe(
+      "Search for documents matching a text query. " +
+        "IMPORTANT: The 'query' argument is required. " +
+        "Example: { query: 'meeting notes' }",
+    ),
     async ({ arguments: args }) => {
       const query = new URLSearchParams({
         query: args.query,
@@ -245,10 +282,13 @@ export function registerLocalRestApiTools(tools: ToolRegistry, server: Server) {
     type({
       name: '"list_vault_files"',
       arguments: {
-        "directory?": "string",
+        "directory?": type("string").describe(
+          "The vault-relative path to list. Optional, defaults to vault root.",
+        ),
       },
     }).describe(
-      "List files in the root directory or a specified subdirectory of your vault.",
+      "List files in the root directory or a specified subdirectory of your vault. " +
+        "Example: { directory: 'notes/projects' }",
     ),
     async ({ arguments: args }) => {
       const path = args.directory ? `${args.directory}/` : "";
@@ -269,10 +309,18 @@ export function registerLocalRestApiTools(tools: ToolRegistry, server: Server) {
     type({
       name: '"get_vault_file"',
       arguments: {
-        filename: "string",
-        "format?": '"markdown" | "json"',
+        filename: type("string").describe(
+          "The vault-relative path to the file (e.g., 'notes/my-note.md'). REQUIRED.",
+        ),
+        "format?": type('"markdown" | "json"').describe(
+          "Response format: 'markdown' for raw content or 'json' for parsed with frontmatter. Optional, defaults to 'markdown'.",
+        ),
       },
-    }).describe("Get the content of a file from your vault."),
+    }).describe(
+      "Get the content of a file from your vault. " +
+        "IMPORTANT: The 'filename' argument is required. " +
+        "Example: { filename: 'daily/2025-01-17.md' }",
+    ),
     async ({ arguments: args }) => {
       const isJson = args.format === "json";
       const format = isJson
@@ -302,10 +350,18 @@ export function registerLocalRestApiTools(tools: ToolRegistry, server: Server) {
     type({
       name: '"create_vault_file"',
       arguments: {
-        filename: "string",
-        content: "string",
+        filename: type("string").describe(
+          "The vault-relative path to the file (e.g., 'notes/my-note.md'). REQUIRED.",
+        ),
+        content: type("string").describe(
+          "The complete content to write to the file. REQUIRED.",
+        ),
       },
-    }).describe("Create a new file in your vault or update an existing one."),
+    }).describe(
+      "Create a new file in your vault or update an existing file. " +
+        "IMPORTANT: Both 'filename' and 'content' arguments are required. " +
+        "Example: { filename: 'daily/2025-01-17.md', content: '# Daily Note\\n\\nContent here' }",
+    ),
     async ({ arguments: args }) => {
       await makeRequest(
         LocalRestAPI.ApiNoContentResponse,
@@ -326,10 +382,18 @@ export function registerLocalRestApiTools(tools: ToolRegistry, server: Server) {
     type({
       name: '"append_to_vault_file"',
       arguments: {
-        filename: "string",
-        content: "string",
+        filename: type("string").describe(
+          "The vault-relative path to the file (e.g., 'notes/my-note.md'). REQUIRED.",
+        ),
+        content: type("string").describe(
+          "The content to append to the end of the file. REQUIRED.",
+        ),
       },
-    }).describe("Append content to a new or existing file."),
+    }).describe(
+      "Append content to a new or existing file. " +
+        "IMPORTANT: Both 'filename' and 'content' arguments are required. " +
+        "Example: { filename: 'journal/log.md', content: '\\n\\n## New Entry\\n\\nContent here' }",
+    ),
     async ({ arguments: args }) => {
       await makeRequest(
         LocalRestAPI.ApiNoContentResponse,
@@ -350,10 +414,14 @@ export function registerLocalRestApiTools(tools: ToolRegistry, server: Server) {
     type({
       name: '"patch_vault_file"',
       arguments: type({
-        filename: "string",
+        filename: type("string").describe(
+          "The vault-relative path to the file (e.g., 'notes/my-note.md'). REQUIRED.",
+        ),
       }).and(LocalRestAPI.ApiPatchParameters),
     }).describe(
-      "Insert or modify content in a file relative to a heading, block reference, or frontmatter field.",
+      "Insert or modify content in a file relative to a heading, block reference, or frontmatter field. " +
+        "IMPORTANT: The 'filename', 'operation', 'targetType', 'target', and 'content' arguments are required. " +
+        "Example: { filename: 'notes/todo.md', operation: 'append', targetType: 'heading', target: 'Tasks', content: '\\n- [ ] New task' }",
     ),
     async ({ arguments: args }) => {
       const headers: HeadersInit = {
@@ -397,9 +465,15 @@ export function registerLocalRestApiTools(tools: ToolRegistry, server: Server) {
     type({
       name: '"delete_vault_file"',
       arguments: {
-        filename: "string",
+        filename: type("string").describe(
+          "The vault-relative path to the file to delete (e.g., 'notes/old-note.md'). REQUIRED.",
+        ),
       },
-    }).describe("Delete a file from your vault."),
+    }).describe(
+      "Delete a file from your vault. " +
+        "IMPORTANT: The 'filename' argument is required. " +
+        "Example: { filename: 'archive/old-note.md' }",
+    ),
     async ({ arguments: args }) => {
       await makeRequest(
         LocalRestAPI.ApiNoContentResponse,
diff --git a/packages/mcp-server/src/features/smart-connections/index.ts b/packages/mcp-server/src/features/smart-connections/index.ts
index b017d16..7914752 100644
--- a/packages/mcp-server/src/features/smart-connections/index.ts
+++ b/packages/mcp-server/src/features/smart-connections/index.ts
@@ -7,20 +7,26 @@ export function registerSmartConnectionsTools(tools: ToolRegistry) {
     type({
       name: '"search_vault_smart"',
       arguments: {
-        query: type("string>0").describe("A search phrase for semantic search"),
+        query: type("string>0").describe(
+          "A search phrase for semantic search. REQUIRED.",
+        ),
         "filter?": {
           "folders?": type("string[]").describe(
-            'An array of folder names to include. For example, ["Public", "Work"]',
+            "An array of folder names to include. For example, ['Public', 'Work']. Optional.",
           ),
           "excludeFolders?": type("string[]").describe(
-            'An array of folder names to exclude. For example, ["Private", "Archive"]',
+            "An array of folder names to exclude. For example, ['Private', 'Archive']. Optional.",
           ),
           "limit?": type("number>0").describe(
-            "The maximum number of results to return",
+            "The maximum number of results to return. Optional.",
           ),
         },
       },
-    }).describe("Search for documents semantically matching a text string."),
+    }).describe(
+      "Search for documents semantically matching a text string. " +
+        "IMPORTANT: The 'query' argument is required. " +
+        "Example: { query: 'meeting notes about project planning', filter: { folders: ['Work'], limit: 10 } }",
+    ),
     async ({ arguments: args }) => {
       const data = await makeRequest(
         LocalRestAPI.ApiSmartSearchResponse,
diff --git a/packages/mcp-server/src/features/templates/index.ts b/packages/mcp-server/src/features/templates/index.ts
index 60b7722..37d9a66 100644
--- a/packages/mcp-server/src/features/templates/index.ts
+++ b/packages/mcp-server/src/features/templates/index.ts
@@ -14,10 +14,16 @@ export function registerTemplaterTools(tools: ToolRegistry) {
       arguments: LocalRestAPI.ApiTemplateExecutionParams.omit("createFile").and(
         {
           // should be boolean but the MCP client returns a string
-          "createFile?": type("'true'|'false'"),
+          "createFile?": type("'true'|'false'").describe(
+            "Whether to create a new file from the template. Optional.",
+          ),
         },
       ),
-    }).describe("Execute a Templater template with the given arguments"),
+    }).describe(
+      "Execute a Templater template with the given arguments. " +
+        "IMPORTANT: The 'name' argument is required. " +
+        "Example: { name: 'templates/daily-note.md', arguments: { title: 'My Title' }, createFile: 'true', targetPath: 'notes/output.md' }",
+    ),
     async ({ arguments: args }) => {
       // Get prompt content
       const data = await makeRequest(
diff --git a/packages/mcp-server/src/shared/ToolRegistry.ts b/packages/mcp-server/src/shared/ToolRegistry.ts
index 14dd574..c260d31 100644
--- a/packages/mcp-server/src/shared/ToolRegistry.ts
+++ b/packages/mcp-server/src/shared/ToolRegistry.ts
@@ -124,6 +124,16 @@ export class ToolRegistryClass<
     context: HandlerContext,
   ) => {
     try {
+      const argCount = params.arguments
+        ? Object.keys(params.arguments).length
+        : 0;
+      if (argCount === 0) {
+        logger.warn(`Tool "${params.name}" called with no arguments`, {
+          name: params.name,
+          arguments: params.arguments,
+        });
+      }
+
       for (const [schema, handler] of this.entries()) {
         if (schema.get("name").allows(params.name)) {
           const validParams = schema.assert(
diff --git a/packages/mcp-server/src/shared/formatMcpError.ts b/packages/mcp-server/src/shared/formatMcpError.ts
index c408c06..12e8423 100644
--- a/packages/mcp-server/src/shared/formatMcpError.ts
+++ b/packages/mcp-server/src/shared/formatMcpError.ts
@@ -8,7 +8,10 @@ export function formatMcpError(error: unknown) {
 
   if (error instanceof type.errors) {
     const message = error.summary;
-    return new McpError(ErrorCode.InvalidParams, message);
+    const hint = message.includes("must be")
+      ? " HINT: Ensure all required parameters are included in the arguments object."
+      : "";
+    return new McpError(ErrorCode.InvalidParams, message + hint);
   }
 
   if (type({ message: "string" }).allows(error)) {
diff --git a/packages/shared/src/types/plugin-local-rest-api.ts b/packages/shared/src/types/plugin-local-rest-api.ts
index 3f7a216..c0cab66 100644
--- a/packages/shared/src/types/plugin-local-rest-api.ts
+++ b/packages/shared/src/types/plugin-local-rest-api.ts
@@ -258,13 +258,17 @@ export const ApiNoContentResponse = type("unknown").describe("No Content");
  * @property targetPath - The path to save the file; required if createFile is true
  */
 export const ApiTemplateExecutionParams = type({
-  name: type("string").describe("The full vault path to the template file"),
-  arguments: "Record<string, string>",
+  name: type("string").describe(
+    "The full vault path to the template file. REQUIRED.",
+  ),
+  arguments: type("Record<string, string>").describe(
+    "Key-value pairs of template parameters. The keys should match tp.mcpTools.prompt() calls in the template.",
+  ),
   "createFile?": type("boolean").describe(
-    "Whether to create a new file from the template",
+    "Whether to create a new file from the template. Optional.",
   ),
   "targetPath?": type("string").describe(
-    "Path to save the file; required if createFile is true",
+    "Path to save the file; required if createFile is true. Optional.",
   ),
 });