feat(skill_mcp): add dynamic truncation and grep filtering

- Add skill_mcp and webfetch to TRUNCATABLE_TOOLS list
- Add grep parameter for regex filtering of output lines
- Prevents token overflow from large MCP responses

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

Author: code-yeongyu

src/hooks/tool-output-truncator.ts

@@ -16,6 +16,9 @@ const TRUNCATABLE_TOOLS = [
   "ast_grep_search",
   "interactive_bash",
   "Interactive_bash",
+  "skill_mcp",
+  "webfetch",
+  "WebFetch",
 ]
 
 interface ToolOutputTruncatorOptions {

src/tools/skill-mcp/tools.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect, beforeEach, mock } from "bun:test"
-import { createSkillMcpTool } from "./tools"
+import { createSkillMcpTool, applyGrepFilter } from "./tools"
 import { SkillMcpManager } from "../../features/skill-mcp-manager"
 import type { LoadedSkill } from "../../features/opencode-skill-loader/types"
 
@@ -147,5 +147,69 @@ describe("skill_mcp tool", () => {
       expect(tool.description.length).toBeLessThan(200)
       expect(tool.description).toContain("mcp_name")
     })
+
+    it("includes grep parameter in schema", () => {
+      // #given / #when
+      const tool = createSkillMcpTool({
+        manager,
+        getLoadedSkills: () => [],
+        getSessionID: () => "session",
+      })
+
+      // #then
+      expect(tool.description).toBeDefined()
+    })
+  })
+})
+
+describe("applyGrepFilter", () => {
+  it("filters lines matching pattern", () => {
+    // #given
+    const output = `line1: hello world
+line2: foo bar
+line3: hello again
+line4: baz qux`
+
+    // #when
+    const result = applyGrepFilter(output, "hello")
+
+    // #then
+    expect(result).toContain("line1: hello world")
+    expect(result).toContain("line3: hello again")
+    expect(result).not.toContain("foo bar")
+    expect(result).not.toContain("baz qux")
+  })
+
+  it("returns original output when pattern is undefined", () => {
+    // #given
+    const output = "some output"
+
+    // #when
+    const result = applyGrepFilter(output, undefined)
+
+    // #then
+    expect(result).toBe(output)
+  })
+
+  it("returns message when no lines match", () => {
+    // #given
+    const output = "line1\nline2\nline3"
+
+    // #when
+    const result = applyGrepFilter(output, "xyz")
+
+    // #then
+    expect(result).toContain("[grep] No lines matched pattern")
+  })
+
+  it("handles invalid regex gracefully", () => {
+    // #given
+    const output = "some output"
+
+    // #when
+    const result = applyGrepFilter(output, "[invalid")
+
+    // #then
+    expect(result).toBe(output)
   })
 })

src/tools/skill-mcp/tools.ts

@@ -87,6 +87,20 @@ function parseArguments(argsJson: string | undefined): Record<string, unknown> {
   }
 }
 
+export function applyGrepFilter(output: string, pattern: string | undefined): string {
+  if (!pattern) return output
+  try {
+    const regex = new RegExp(pattern, "i")
+    const lines = output.split("\n")
+    const filtered = lines.filter(line => regex.test(line))
+    return filtered.length > 0 
+      ? filtered.join("\n") 
+      : `[grep] No lines matched pattern: ${pattern}`
+  } catch {
+    return output
+  }
+}
+
 export function createSkillMcpTool(options: SkillMcpToolOptions): ToolDefinition {
   const { manager, getLoadedSkills, getSessionID } = options
 
@@ -98,6 +112,7 @@ export function createSkillMcpTool(options: SkillMcpToolOptions): ToolDefinition
       resource_name: tool.schema.string().optional().describe("MCP resource URI to read"),
       prompt_name: tool.schema.string().optional().describe("MCP prompt to get"),
       arguments: tool.schema.string().optional().describe("JSON string of arguments"),
+      grep: tool.schema.string().optional().describe("Regex pattern to filter output lines (only matching lines returned)"),
     },
     async execute(args: SkillMcpArgs) {
       const operation = validateOperationParams(args)
@@ -126,24 +141,29 @@ export function createSkillMcpTool(options: SkillMcpToolOptions): ToolDefinition
 
       const parsedArgs = parseArguments(args.arguments)
 
+      let output: string
       switch (operation.type) {
         case "tool": {
           const result = await manager.callTool(info, context, operation.name, parsedArgs)
-          return JSON.stringify(result, null, 2)
+          output = JSON.stringify(result, null, 2)
+          break
         }
         case "resource": {
           const result = await manager.readResource(info, context, operation.name)
-          return JSON.stringify(result, null, 2)
+          output = JSON.stringify(result, null, 2)
+          break
         }
         case "prompt": {
           const stringArgs: Record<string, string> = {}
           for (const [key, value] of Object.entries(parsedArgs)) {
             stringArgs[key] = String(value)
           }
           const result = await manager.getPrompt(info, context, operation.name, stringArgs)
-          return JSON.stringify(result, null, 2)
+          output = JSON.stringify(result, null, 2)
+          break
         }
       }
+      return applyGrepFilter(output, args.grep)
     },
   })
 }

src/tools/skill-mcp/types.ts

@@ -4,4 +4,5 @@ export interface SkillMcpArgs {
   resource_name?: string
   prompt_name?: string
   arguments?: string
+  grep?: string
 }