Parse tool args from CLI as JsonValue instead of just strings

Author: olaservo

cli/src/client/prompts.ts

@@ -1,6 +1,16 @@
 import { Client } from "@modelcontextprotocol/sdk/client/index.js";
 import { McpResponse } from "./types.js";
 
+// JSON value type matching the client utils
+type JsonValue =
+  | string
+  | number
+  | boolean
+  | null
+  | undefined
+  | JsonValue[]
+  | { [key: string]: JsonValue };
+
 // List available prompts
 export async function listPrompts(client: Client): Promise<McpResponse> {
   try {
@@ -17,12 +27,26 @@ export async function listPrompts(client: Client): Promise<McpResponse> {
 export async function getPrompt(
   client: Client,
   name: string,
-  args?: Record<string, string>,
+  args?: Record<string, JsonValue>,
 ): Promise<McpResponse> {
   try {
+    // Convert all arguments to strings for prompt arguments
+    const stringArgs: Record<string, string> = {};
+    if (args) {
+      for (const [key, value] of Object.entries(args)) {
+        if (typeof value === 'string') {
+          stringArgs[key] = value;
+        } else if (value === null || value === undefined) {
+          stringArgs[key] = String(value);
+        } else {
+          stringArgs[key] = JSON.stringify(value);
+        }
+      }
+    }
+
     const response = await client.getPrompt({
       name,
-      arguments: args || {},
+      arguments: stringArgs,
     });
 
     return response;

cli/src/client/tools.ts

@@ -2,6 +2,16 @@ import { Client } from "@modelcontextprotocol/sdk/client/index.js";
 import { Tool } from "@modelcontextprotocol/sdk/types.js";
 import { McpResponse } from "./types.js";
 
+// JSON value type matching the client utils
+type JsonValue =
+  | string
+  | number
+  | boolean
+  | null
+  | undefined
+  | JsonValue[]
+  | { [key: string]: JsonValue };
+
 type JsonSchemaType = {
   type: "string" | "number" | "integer" | "boolean" | "array" | "object";
   description?: string;
@@ -20,7 +30,7 @@ export async function listTools(client: Client): Promise<McpResponse> {
   }
 }
 
-function convertParameterValue(value: string, schema: JsonSchemaType): unknown {
+function convertParameterValue(value: string, schema: JsonSchemaType): JsonValue {
   if (!value) {
     return value;
   }
@@ -35,7 +45,7 @@ function convertParameterValue(value: string, schema: JsonSchemaType): unknown {
 
   if (schema.type === "object" || schema.type === "array") {
     try {
-      return JSON.parse(value);
+      return JSON.parse(value) as JsonValue;
     } catch (error) {
       return value;
     }
@@ -47,8 +57,8 @@ function convertParameterValue(value: string, schema: JsonSchemaType): unknown {
 function convertParameters(
   tool: Tool,
   params: Record<string, string>,
-): Record<string, unknown> {
-  const result: Record<string, unknown> = {};
+): Record<string, JsonValue> {
+  const result: Record<string, JsonValue> = {};
   const properties = tool.inputSchema.properties || {};
 
   for (const [key, value] of Object.entries(params)) {
@@ -68,18 +78,29 @@ function convertParameters(
 export async function callTool(
   client: Client,
   name: string,
-  args: Record<string, string>,
+  args: Record<string, JsonValue>,
 ): Promise<McpResponse> {
   try {
     const toolsResponse = await listTools(client);
     const tools = toolsResponse.tools as Tool[];
     const tool = tools.find((t) => t.name === name);
 
-    let convertedArgs: Record<string, unknown> = args;
+    let convertedArgs: Record<string, JsonValue> = args;
 
     if (tool) {
-      // Convert parameters based on the tool's schema
-      convertedArgs = convertParameters(tool, args);
+      // Convert parameters based on the tool's schema, but only for string values
+      // since we now accept pre-parsed values from the CLI
+      const stringArgs: Record<string, string> = {};
+      for (const [key, value] of Object.entries(args)) {
+        if (typeof value === 'string') {
+          stringArgs[key] = value;
+        }
+      }
+      
+      if (Object.keys(stringArgs).length > 0) {
+        const convertedStringArgs = convertParameters(tool, stringArgs);
+        convertedArgs = { ...args, ...convertedStringArgs };
+      }
     }
 
     const response = await client.callTool({

cli/src/index.ts

@@ -20,15 +20,25 @@ import {
 import { handleError } from "./error-handler.js";
 import { createTransport, TransportOptions } from "./transport.js";
 
+// JSON value type for CLI arguments
+type JsonValue =
+  | string
+  | number
+  | boolean
+  | null
+  | undefined
+  | JsonValue[]
+  | { [key: string]: JsonValue };
+
 type Args = {
   target: string[];
   method?: string;
   promptName?: string;
-  promptArgs?: Record<string, string>;
+  promptArgs?: Record<string, JsonValue>;
   uri?: string;
   logLevel?: LogLevel;
   toolName?: string;
-  toolArg?: Record<string, string>;
+  toolArg?: Record<string, JsonValue>;
   transport?: "sse" | "stdio" | "http";
 };
 
@@ -162,8 +172,8 @@ async function callMethod(args: Args): Promise<void> {
 
 function parseKeyValuePair(
   value: string,
-  previous: Record<string, string> = {},
-): Record<string, string> {
+  previous: Record<string, JsonValue> = {},
+): Record<string, JsonValue> {
   const parts = value.split("=");
   const key = parts[0];
   const val = parts.slice(1).join("=");
@@ -174,7 +184,16 @@ function parseKeyValuePair(
     );
   }
 
-  return { ...previous, [key as string]: val };
+  // Try to parse as JSON first
+  let parsedValue: JsonValue;
+  try {
+    parsedValue = JSON.parse(val) as JsonValue;
+  } catch {
+    // If JSON parsing fails, keep as string
+    parsedValue = val;
+  }
+
+  return { ...previous, [key as string]: parsedValue };
 }
 
 function parseArgs(): Args {