fix(mcp): tolerate output schema ref failures (#26614)

packages/opencode/src/mcp/index.ts

@@ -6,6 +6,7 @@ import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js"
 import { UnauthorizedError } from "@modelcontextprotocol/sdk/client/auth.js"
 import {
   CallToolResultSchema,
+  ToolSchema,
   type Tool as MCPToolDef,
   ToolListChangedNotificationSchema,
 } from "@modelcontextprotocol/sdk/types.js"
@@ -36,6 +37,15 @@ import { withStatics } from "@opencode-ai/core/schema"
 const log = Log.create({ service: "mcp" })
 const DEFAULT_TIMEOUT = 30_000
 
+const TolerantToolSchema = ToolSchema.extend({
+  outputSchema: z.unknown().optional(),
+})
+
+const TolerantListToolsResultSchema = z.looseObject({
+  tools: z.array(TolerantToolSchema),
+  nextCursor: z.string().optional(),
+})
+
 export const Resource = Schema.Struct({
   name: Schema.String,
   uri: Schema.String,
@@ -119,6 +129,38 @@ function remoteURL(key: string, value: string) {
   log.warn("invalid remote mcp url", { key })
 }
 
+function isOutputSchemaValidationError(error: Error) {
+  return /can't resolve reference|resolves to more than one schema|outputSchema|schema.*reference|reference.*schema/i.test(
+    error.message,
+  )
+}
+
+function listTools(key: string, client: MCPClient, timeout: number) {
+  return Effect.tryPromise({
+    try: () => client.listTools(undefined, { timeout }),
+    catch: (err) => (err instanceof Error ? err : new Error(String(err))),
+  }).pipe(
+    Effect.map((result) => result.tools),
+    Effect.catch((error) => {
+      if (!isOutputSchemaValidationError(error)) return Effect.fail(error)
+
+      log.warn("failed to validate MCP tool output schemas, retrying without output schema validation", { key, error })
+      return Effect.tryPromise({
+        try: () => client.request({ method: "tools/list" }, TolerantListToolsResultSchema, { timeout }),
+        catch: (err) => (err instanceof Error ? err : new Error(String(err))),
+      }).pipe(
+        Effect.map((result) =>
+          result.tools.map((tool) => ({
+            name: tool.name,
+            description: tool.description,
+            inputSchema: tool.inputSchema,
+          })),
+        ),
+      )
+    }),
+  )
+}
+
 // Convert MCP tool definition to AI SDK Tool type
 function convertMcpTool(mcpTool: MCPToolDef, client: MCPClient, timeout?: number): Tool {
   const inputSchema = mcpTool.inputSchema
@@ -151,11 +193,7 @@ function convertMcpTool(mcpTool: MCPToolDef, client: MCPClient, timeout?: number
 }
 
 function defs(key: string, client: MCPClient, timeout?: number) {
-  return Effect.tryPromise({
-    try: () => withTimeout(client.listTools(), timeout ?? DEFAULT_TIMEOUT),
-    catch: (err) => (err instanceof Error ? err : new Error(String(err))),
-  }).pipe(
-    Effect.map((result) => result.tools),
+  return listTools(key, client, timeout ?? DEFAULT_TIMEOUT).pipe(
     Effect.catch((err) => {
       log.error("failed to get tools from client", { key, error: err })
       return Effect.succeed(undefined)