diff --git a/packages/builtin-tools/src/tools/SearchExtraToolsTool/SearchExtraToolsTool.ts b/packages/builtin-tools/src/tools/SearchExtraToolsTool/SearchExtraToolsTool.ts
index 5fa35649f..95c5cbe77 100644
--- a/packages/builtin-tools/src/tools/SearchExtraToolsTool/SearchExtraToolsTool.ts
+++ b/packages/builtin-tools/src/tools/SearchExtraToolsTool/SearchExtraToolsTool.ts
@@ -58,6 +58,17 @@ export const outputSchema = lazySchema(() =>
     pending_mcp_servers: z.array(z.string()).optional(),
     /** Matches that are already loaded (core tools) and can be called directly. */
     already_loaded: z.array(z.string()).optional(),
+    /** Tool details (name, description, schema) for discover mode. */
+    details: z
+      .array(
+        z.object({
+          name: z.string(),
+          description: z.string(),
+          score: z.number(),
+          inputSchema: z.record(z.string(), z.unknown()).optional(),
+        }),
+      )
+      .optional(),
   }),
 )
 type OutputSchema = ReturnType<typeof outputSchema>
@@ -131,6 +142,7 @@ function buildSearchResult(
   totalDeferredTools: number,
   pendingMcpServers?: string[],
   alreadyLoaded?: string[],
+  details?: Output['details'],
 ): { data: Output } {
   return {
     data: {
@@ -143,6 +155,7 @@ function buildSearchResult(
       ...(alreadyLoaded && alreadyLoaded.length > 0
         ? { already_loaded: alreadyLoaded }
         : {}),
+      ...(details && details.length > 0 ? { details } : {}),
     },
   }
 }
@@ -446,17 +459,12 @@ export const SearchExtraToolsTool = buildTool({
       const discoverQuery = discoverMatch[1]!.trim()
       const index = await getToolIndex(deferredTools)
       const tfIdfResults = searchTools(discoverQuery, index, max_results)
-      const textResults = tfIdfResults.map(r => {
-        let line = `**${r.name}** (score: ${r.score.toFixed(2)})\n${r.description}`
-        if (r.inputSchema) {
-          line += `\nSchema: ${JSON.stringify(r.inputSchema)}`
-        }
-        return line
-      })
-      const text =
-        textResults.length > 0
-          ? `Found ${textResults.length} tools:\n${textResults.join('\n\n')}`
-          : 'No matching deferred tools found'
+      const details = tfIdfResults.map(r => ({
+        name: r.name,
+        description: r.description,
+        score: r.score,
+        ...(r.inputSchema ? { inputSchema: r.inputSchema as Record<string, unknown> } : {}),
+      }))
       logSearchOutcome(
         tfIdfResults.map(r => r.name),
         'keyword',
@@ -465,6 +473,9 @@ export const SearchExtraToolsTool = buildTool({
         tfIdfResults.map(r => r.name),
         query,
         deferredTools.length,
+        undefined,
+        undefined,
+        details,
       )
     }
 
@@ -559,6 +570,26 @@ export const SearchExtraToolsTool = buildTool({
       }
     }
 
+    // Discover mode: render tool details with name, description, and input schema.
+    // This lets the model inspect parameters before selecting and invoking a tool.
+    if (content.details && content.details.length > 0) {
+      const lines = content.details.map(d => {
+        let line = `**${d.name}** (score: ${d.score.toFixed(2)})\n${d.description}`
+        if (d.inputSchema) {
+          line += `\nSchema: ${JSON.stringify(d.inputSchema)}`
+        }
+        return line
+      })
+      const text =
+        `Found ${lines.length} tool(s) matching your query:\n\n` +
+        lines.join('\n\n')
+      return {
+        type: 'tool_result',
+        tool_use_id: toolUseID,
+        content: text,
+      }
+    }
+
     // Separate already-loaded (core) tools from truly deferred tools
     const alreadyLoadedNames = content.already_loaded ?? []
     const deferredNames = content.matches.filter(
diff --git a/packages/builtin-tools/src/tools/SearchExtraToolsTool/__tests__/SearchExtraToolsTool.test.ts b/packages/builtin-tools/src/tools/SearchExtraToolsTool/__tests__/SearchExtraToolsTool.test.ts
index e8faed328..627d5463e 100644
--- a/packages/builtin-tools/src/tools/SearchExtraToolsTool/__tests__/SearchExtraToolsTool.test.ts
+++ b/packages/builtin-tools/src/tools/SearchExtraToolsTool/__tests__/SearchExtraToolsTool.test.ts
@@ -101,7 +101,7 @@ function makeContext(tools: unknown[] = []) {
 }
 
 describe('SearchExtraToolsTool search enhancements', () => {
-  test('discover: prefix triggers TF-IDF search and returns matches', async () => {
+  test('discover: prefix triggers TF-IDF search and returns matches with details', async () => {
     const mockTool = makeDeferredTool('CronCreate', 'Schedule cron jobs')
     mockGetToolIndex.mockResolvedValueOnce([])
     mockSearchTools.mockReturnValueOnce([
@@ -112,11 +112,11 @@ describe('SearchExtraToolsTool search enhancements', () => {
         score: 0.85,
         isMcp: false,
         isDeferred: true,
-        inputSchema: undefined,
+        inputSchema: { interval: { type: 'string' } },
       },
     ])
 
-    const result: { data: { matches: string[] } } = await (
+    const result: { data: { matches: string[]; details?: Array<{ name: string; description: string; score: number; inputSchema?: Record<string, unknown> }> } } = await (
       SearchExtraToolsTool as any
     ).call(
       { query: 'discover:schedule cron job', max_results: 5 },
@@ -127,6 +127,11 @@ describe('SearchExtraToolsTool search enhancements', () => {
     )
 
     expect(result.data.matches).toContain('CronCreate')
+    expect(result.data.details).toBeDefined()
+    expect(result.data.details!.length).toBe(1)
+    expect(result.data.details![0]!.name).toBe('CronCreate')
+    expect(result.data.details![0]!.description).toBe('Schedule cron jobs')
+    expect(result.data.details![0]!.inputSchema).toEqual({ interval: { type: 'string' } })
   })
 
   test('keyword + TF-IDF parallel search merges results', async () => {
@@ -232,4 +237,29 @@ describe('SearchExtraToolsTool search enhancements', () => {
 
     expect(blockParam.content).toContain('No matching deferred tools found')
   })
+
+  test('discover mode renders details with description and schema', async () => {
+    const blockParam = SearchExtraToolsTool.mapToolResultToToolResultBlockParam(
+      {
+        matches: ['CronCreate'],
+        query: 'discover:schedule',
+        total_deferred_tools: 5,
+        details: [
+          {
+            name: 'CronCreate',
+            description: 'Schedule cron jobs',
+            score: 0.85,
+            inputSchema: { interval: { type: 'string' } },
+          },
+        ],
+      },
+      'tool-use-123',
+    )
+
+    expect(typeof blockParam.content).toBe('string')
+    expect(blockParam.content as string).toContain('CronCreate')
+    expect(blockParam.content as string).toContain('Schedule cron jobs')
+    expect(blockParam.content as string).toContain('Schema')
+    expect(blockParam.content as string).toContain('"interval"')
+  })
 })
diff --git a/packages/builtin-tools/src/tools/SearchExtraToolsTool/prompt.ts b/packages/builtin-tools/src/tools/SearchExtraToolsTool/prompt.ts
index 6f66c192a..1bf7a0a11 100644
--- a/packages/builtin-tools/src/tools/SearchExtraToolsTool/prompt.ts
+++ b/packages/builtin-tools/src/tools/SearchExtraToolsTool/prompt.ts
@@ -29,7 +29,7 @@ IMPORTANT: ExecuteExtraTool is always available in your tool list. After this se
 
 Query forms:
 - "select:CronCreate,Snip" — fetch these exact tools by name
-- "discover:schedule cron job" — pure discovery, returns tool info (name, description) without loading. Use when you want to understand available tools before deciding which to invoke.
+- "discover:schedule cron job" — pure discovery, returns tool info (name, description, input schema) without loading. Use when you need to understand a tool's parameters before invoking it, then call ExecuteExtraTool with the discovered tool name and params.
 - "notebook jupyter" — keyword search, up to max_results best matches
 - "+slack send" — require "slack" in the name, rank by remaining terms`