diff --git a/packages/opencode/src/mcp/index.ts b/packages/opencode/src/mcp/index.ts
index 1b6c9bb5fe..0d6c8c65dc 100644
--- a/packages/opencode/src/mcp/index.ts
+++ b/packages/opencode/src/mcp/index.ts
@@ -210,6 +210,10 @@ const layer = Layer.effect(
 
     type Transport = StdioClientTransport | StreamableHTTPClientTransport | SSEClientTransport
 
+    /**
+     * Connect a client via the given transport with resource safety:
+     * on failure the transport is closed; on success the caller owns it.
+     */
     const connectTransport = Effect.fn("MCP.connectTransport")(function* (transport: Transport, timeout: number) {
       const directory = yield* InstanceState.directory
       return yield* Effect.acquireUseRelease(
diff --git a/packages/opencode/test/session/prompt.test.ts b/packages/opencode/test/session/prompt.test.ts
index 01b1af5b99..491ad06aaf 100644
--- a/packages/opencode/test/session/prompt.test.ts
+++ b/packages/opencode/test/session/prompt.test.ts
@@ -117,7 +117,6 @@ function makeMcp(instructions: MCP.ServerInstructions[] = []) {
       clients: () => Effect.succeed({}),
       instructions: () => Effect.succeed(instructions),
       tools: () => Effect.succeed({}),
-      defs: () => Effect.succeed({}),
       prompts: () => Effect.succeed({}),
       resources: () => Effect.succeed({}),
       resourceTemplates: () => Effect.succeed({}),
diff --git a/packages/opencode/test/session/snapshot-tool-race.test.ts b/packages/opencode/test/session/snapshot-tool-race.test.ts
index 3bbb4b1fc5..1265237840 100644
--- a/packages/opencode/test/session/snapshot-tool-race.test.ts
+++ b/packages/opencode/test/session/snapshot-tool-race.test.ts
@@ -39,7 +39,6 @@ const mcp = Layer.succeed(
     clients: () => Effect.succeed({}),
     instructions: () => Effect.succeed([]),
     tools: () => Effect.succeed({}),
-    defs: () => Effect.succeed({}),
     prompts: () => Effect.succeed({}),
     resources: () => Effect.succeed({}),
     resourceTemplates: () => Effect.succeed({}),
diff --git a/packages/opencode/test/tool/code-mode-integration.test.ts b/packages/opencode/test/tool/code-mode-integration.test.ts
index f9ed25a831..c4553b4c79 100644
--- a/packages/opencode/test/tool/code-mode-integration.test.ts
+++ b/packages/opencode/test/tool/code-mode-integration.test.ts
@@ -17,7 +17,6 @@ import {
   ListToolsRequestSchema,
   type Tool as MCPToolDef,
 } from "@modelcontextprotocol/sdk/types.js"
-import type { Tool as AITool } from "ai"
 import { Effect, Layer } from "effect"
 
 const PNG =
@@ -135,12 +134,9 @@ async function buildTool() {
   await client.connect()
 
   const listed = (await client.listTools()).tools as MCPToolDef[]
-  const mcpTools: Record<string, AITool> = {}
-  const mcpDefs: Record<string, MCPToolDef> = {}
+  const mcpTools: Record<string, MCP.McpTool> = {}
   for (const def of listed) {
-    const key = McpCatalog.toolName(SERVER, def.name)
-    mcpDefs[key] = def
-    mcpTools[key] = McpCatalog.convertTool(def, client as unknown as Client)
+    mcpTools[McpCatalog.toolName(SERVER, def.name)] = { def, client: client as unknown as Client }
   }
 
   const layer = Layer.mergeAll(
@@ -155,13 +151,12 @@ async function buildTool() {
     Layer.mock(Session.Service, { get: () => Effect.succeed({ permission: [] } as any) }),
     Layer.mock(MCP.Service, {
       tools: () => Effect.succeed(mcpTools),
-      defs: () => Effect.succeed(mcpDefs),
       clients: () => Effect.succeed({ [SERVER]: {} as any }),
     }),
   )
   return {
     tool: await Effect.runPromise(CodeModeTool.pipe(Effect.flatMap(Tool.init), Effect.provide(layer))),
-    description: describeCatalog(mcpTools, mcpDefs, [SERVER]),
+    description: describeCatalog(mcpTools, [SERVER]),
   }
 }