feat(coding-agent): type ToolCallEvent.input per tool (#1147)

packages/coding-agent/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Added
 
+- Added typed `ToolCallEvent.input` per tool with `isToolCallEventType()` type guard for narrowing built-in tool events ([#1147](https://github.com/badlogic/pi-mono/pull/1147) by [@giuseppeg](https://github.com/giuseppeg))
 - Exported `discoverAndLoadExtensions` from package to enable extension testing without a local repo clone ([#1148](https://github.com/badlogic/pi-mono/issues/1148))
 - Added Extension UI Protocol documentation to RPC docs covering all request/response types for extension dialogs and notifications ([#1144](https://github.com/badlogic/pi-mono/pull/1144) by [@aliou](https://github.com/aliou))
 - Added `rpc-demo.ts` example extension exercising all RPC-supported extension UI methods ([#1144](https://github.com/badlogic/pi-mono/pull/1144) by [@aliou](https://github.com/aliou))

packages/coding-agent/docs/extensions.md

@@ -473,16 +473,49 @@ Use this to update UI elements (status bars, footers) or perform model-specific
 
 #### tool_call
 
-Fired before tool executes. **Can block.**
+Fired before tool executes. **Can block.** Use `isToolCallEventType` to narrow and get typed inputs.
 
 ```typescript
+import { isToolCallEventType } from "@mariozechner/pi-coding-agent";
+
 pi.on("tool_call", async (event, ctx) => {
   // event.toolName - "bash", "read", "write", "edit", etc.
   // event.toolCallId
   // event.input - tool parameters
 
-  if (shouldBlock(event)) {
-    return { block: true, reason: "Not allowed" };
+  // Built-in tools: no type params needed
+  if (isToolCallEventType("bash", event)) {
+    // event.input is { command: string; timeout?: number }
+    if (event.input.command.includes("rm -rf")) {
+      return { block: true, reason: "Dangerous command" };
+    }
+  }
+
+  if (isToolCallEventType("read", event)) {
+    // event.input is { path: string; offset?: number; limit?: number }
+    console.log(`Reading: ${event.input.path}`);
+  }
+});
+```
+
+#### Typing custom tool input
+
+Custom tools should export their input type:
+
+```typescript
+// my-extension.ts
+export type MyToolInput = Static<typeof myToolSchema>;
+```
+
+Use `isToolCallEventType` with explicit type parameters:
+
+```typescript
+import { isToolCallEventType } from "@mariozechner/pi-coding-agent";
+import type { MyToolInput } from "my-extension";
+
+pi.on("tool_call", (event) => {
+  if (isToolCallEventType<"my_tool", MyToolInput>("my_tool", event)) {
+    event.input.action;  // typed
   }
 });
 ```

packages/coding-agent/src/core/extensions/index.ts

@@ -25,6 +25,8 @@ export type {
 	// App keybindings (for custom editors)
 	AppAction,
 	AppendEntryHandler,
+	// Events - Tool (ToolCallEvent types)
+	BashToolCallEvent,
 	BashToolResultEvent,
 	BeforeAgentStartEvent,
 	BeforeAgentStartEventResult,
@@ -35,7 +37,9 @@ export type {
 	// Event Results
 	ContextEventResult,
 	ContextUsage,
+	CustomToolCallEvent,
 	CustomToolResultEvent,
+	EditToolCallEvent,
 	EditToolResultEvent,
 	ExecOptions,
 	ExecResult,
@@ -59,10 +63,12 @@ export type {
 	ExtensionUIContext,
 	ExtensionUIDialogOptions,
 	ExtensionWidgetOptions,
+	FindToolCallEvent,
 	FindToolResultEvent,
 	GetActiveToolsHandler,
 	GetAllToolsHandler,
 	GetThinkingLevelHandler,
+	GrepToolCallEvent,
 	GrepToolResultEvent,
 	// Events - Input
 	InputEvent,
@@ -70,6 +76,7 @@ export type {
 	InputSource,
 	KeybindingsManager,
 	LoadExtensionsResult,
+	LsToolCallEvent,
 	LsToolResultEvent,
 	// Message Rendering
 	MessageRenderer,
@@ -79,6 +86,7 @@ export type {
 	// Provider Registration
 	ProviderConfig,
 	ProviderModelConfig,
+	ReadToolCallEvent,
 	ReadToolResultEvent,
 	// Commands
 	RegisteredCommand,
@@ -124,6 +132,7 @@ export type {
 	UserBashEvent,
 	UserBashEventResult,
 	WidgetPlacement,
+	WriteToolCallEvent,
 	WriteToolResultEvent,
 } from "./types.js";
 // Type guards
@@ -134,6 +143,7 @@ export {
 	isGrepToolResult,
 	isLsToolResult,
 	isReadToolResult,
+	isToolCallEventType,
 	isWriteToolResult,
 } from "./types.js";
 export {

packages/coding-agent/src/core/extensions/types.ts

@@ -57,10 +57,17 @@ import type { BashOperations } from "../tools/bash.js";
 import type { EditToolDetails } from "../tools/edit.js";
 import type {
 	BashToolDetails,
+	BashToolInput,
+	EditToolInput,
 	FindToolDetails,
+	FindToolInput,
 	GrepToolDetails,
+	GrepToolInput,
 	LsToolDetails,
+	LsToolInput,
 	ReadToolDetails,
+	ReadToolInput,
+	WriteToolInput,
 } from "../tools/index.js";
 
 export type { ExecOptions, ExecResult } from "../exec.js";
@@ -547,14 +554,62 @@ export type InputEventResult =
 // Tool Events
 // ============================================================================
 
-/** Fired before a tool executes. Can block. */
-export interface ToolCallEvent {
+interface ToolCallEventBase {
 	type: "tool_call";
-	toolName: string;
 	toolCallId: string;
+}
+
+export interface BashToolCallEvent extends ToolCallEventBase {
+	toolName: "bash";
+	input: BashToolInput;
+}
+
+export interface ReadToolCallEvent extends ToolCallEventBase {
+	toolName: "read";
+	input: ReadToolInput;
+}
+
+export interface EditToolCallEvent extends ToolCallEventBase {
+	toolName: "edit";
+	input: EditToolInput;
+}
+
+export interface WriteToolCallEvent extends ToolCallEventBase {
+	toolName: "write";
+	input: WriteToolInput;
+}
+
+export interface GrepToolCallEvent extends ToolCallEventBase {
+	toolName: "grep";
+	input: GrepToolInput;
+}
+
+export interface FindToolCallEvent extends ToolCallEventBase {
+	toolName: "find";
+	input: FindToolInput;
+}
+
+export interface LsToolCallEvent extends ToolCallEventBase {
+	toolName: "ls";
+	input: LsToolInput;
+}
+
+export interface CustomToolCallEvent extends ToolCallEventBase {
+	toolName: string;
 	input: Record<string, unknown>;
 }
 
+/** Fired before a tool executes. Can block. */
+export type ToolCallEvent =
+	| BashToolCallEvent
+	| ReadToolCallEvent
+	| EditToolCallEvent
+	| WriteToolCallEvent
+	| GrepToolCallEvent
+	| FindToolCallEvent
+	| LsToolCallEvent
+	| CustomToolCallEvent;
+
 interface ToolResultEventBase {
 	type: "tool_result";
 	toolCallId: string;
@@ -614,7 +669,7 @@ export type ToolResultEvent =
 	| LsToolResultEvent
 	| CustomToolResultEvent;
 
-// Type guards
+// Type guards for ToolResultEvent
 export function isBashToolResult(e: ToolResultEvent): e is BashToolResultEvent {
 	return e.toolName === "bash";
 }
@@ -637,6 +692,41 @@ export function isLsToolResult(e: ToolResultEvent): e is LsToolResultEvent {
 	return e.toolName === "ls";
 }
 
+/**
+ * Type guard for narrowing ToolCallEvent by tool name.
+ *
+ * Built-in tools narrow automatically (no type params needed):
+ * ```ts
+ * if (isToolCallEventType("bash", event)) {
+ *   event.input.command;  // string
+ * }
+ * ```
+ *
+ * Custom tools require explicit type parameters:
+ * ```ts
+ * if (isToolCallEventType<"my_tool", MyToolInput>("my_tool", event)) {
+ *   event.input.action;  // typed
+ * }
+ * ```
+ *
+ * Note: Direct narrowing via `event.toolName === "bash"` doesn't work because
+ * CustomToolCallEvent.toolName is `string` which overlaps with all literals.
+ */
+export function isToolCallEventType(toolName: "bash", event: ToolCallEvent): event is BashToolCallEvent;
+export function isToolCallEventType(toolName: "read", event: ToolCallEvent): event is ReadToolCallEvent;
+export function isToolCallEventType(toolName: "edit", event: ToolCallEvent): event is EditToolCallEvent;
+export function isToolCallEventType(toolName: "write", event: ToolCallEvent): event is WriteToolCallEvent;
+export function isToolCallEventType(toolName: "grep", event: ToolCallEvent): event is GrepToolCallEvent;
+export function isToolCallEventType(toolName: "find", event: ToolCallEvent): event is FindToolCallEvent;
+export function isToolCallEventType(toolName: "ls", event: ToolCallEvent): event is LsToolCallEvent;
+export function isToolCallEventType<TName extends string, TInput extends Record<string, unknown>>(
+	toolName: TName,
+	event: ToolCallEvent,
+): event is ToolCallEvent & { toolName: TName; input: TInput };
+export function isToolCallEventType(toolName: string, event: ToolCallEvent): boolean {
+	return event.toolName === toolName;
+}
+
 /** Union of all event types */
 export type ExtensionEvent =
 	| ResourcesDiscoverEvent

packages/coding-agent/src/core/tools/bash.ts

@@ -3,7 +3,7 @@ import { createWriteStream, existsSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 import type { AgentTool } from "@mariozechner/pi-agent-core";
-import { Type } from "@sinclair/typebox";
+import { type Static, Type } from "@sinclair/typebox";
 import { spawn } from "child_process";
 import { getShellConfig, getShellEnv, killProcessTree } from "../../utils/shell.js";
 import { DEFAULT_MAX_BYTES, DEFAULT_MAX_LINES, formatSize, type TruncationResult, truncateTail } from "./truncate.js";
@@ -21,6 +21,8 @@ const bashSchema = Type.Object({
 	timeout: Type.Optional(Type.Number({ description: "Timeout in seconds (optional, no default timeout)" })),
 });
 
+export type BashToolInput = Static<typeof bashSchema>;
+
 export interface BashToolDetails {
 	truncation?: TruncationResult;
 	fullOutputPath?: string;

packages/coding-agent/src/core/tools/edit.ts

@@ -1,5 +1,5 @@
 import type { AgentTool } from "@mariozechner/pi-agent-core";
-import { Type } from "@sinclair/typebox";
+import { type Static, Type } from "@sinclair/typebox";
 import { constants } from "fs";
 import { access as fsAccess, readFile as fsReadFile, writeFile as fsWriteFile } from "fs/promises";
 import {
@@ -19,6 +19,8 @@ const editSchema = Type.Object({
 	newText: Type.String({ description: "New text to replace the old text with" }),
 });
 
+export type EditToolInput = Static<typeof editSchema>;
+
 export interface EditToolDetails {
 	/** Unified diff of the changes made */
 	diff: string;

packages/coding-agent/src/core/tools/find.ts

@@ -1,5 +1,5 @@
 import type { AgentTool } from "@mariozechner/pi-agent-core";
-import { Type } from "@sinclair/typebox";
+import { type Static, Type } from "@sinclair/typebox";
 import { spawnSync } from "child_process";
 import { existsSync } from "fs";
 import { globSync } from "glob";
@@ -16,6 +16,8 @@ const findSchema = Type.Object({
 	limit: Type.Optional(Type.Number({ description: "Maximum number of results (default: 1000)" })),
 });
 
+export type FindToolInput = Static<typeof findSchema>;
+
 const DEFAULT_LIMIT = 1000;
 
 export interface FindToolDetails {

packages/coding-agent/src/core/tools/grep.ts

@@ -1,6 +1,6 @@
 import { createInterface } from "node:readline";
 import type { AgentTool } from "@mariozechner/pi-agent-core";
-import { Type } from "@sinclair/typebox";
+import { type Static, Type } from "@sinclair/typebox";
 import { spawn } from "child_process";
 import { readFileSync, statSync } from "fs";
 import path from "path";
@@ -29,6 +29,8 @@ const grepSchema = Type.Object({
 	limit: Type.Optional(Type.Number({ description: "Maximum number of matches to return (default: 100)" })),
 });
 
+export type GrepToolInput = Static<typeof grepSchema>;
+
 const DEFAULT_LIMIT = 100;
 
 export interface GrepToolDetails {

packages/coding-agent/src/core/tools/index.ts

@@ -1,18 +1,48 @@
 export {
 	type BashOperations,
 	type BashToolDetails,
+	type BashToolInput,
 	type BashToolOptions,
 	bashTool,
 	createBashTool,
 } from "./bash.js";
-export { createEditTool, type EditOperations, type EditToolDetails, type EditToolOptions, editTool } from "./edit.js";
-export { createFindTool, type FindOperations, type FindToolDetails, type FindToolOptions, findTool } from "./find.js";
-export { createGrepTool, type GrepOperations, type GrepToolDetails, type GrepToolOptions, grepTool } from "./grep.js";
-export { createLsTool, type LsOperations, type LsToolDetails, type LsToolOptions, lsTool } from "./ls.js";
+export {
+	createEditTool,
+	type EditOperations,
+	type EditToolDetails,
+	type EditToolInput,
+	type EditToolOptions,
+	editTool,
+} from "./edit.js";
+export {
+	createFindTool,
+	type FindOperations,
+	type FindToolDetails,
+	type FindToolInput,
+	type FindToolOptions,
+	findTool,
+} from "./find.js";
+export {
+	createGrepTool,
+	type GrepOperations,
+	type GrepToolDetails,
+	type GrepToolInput,
+	type GrepToolOptions,
+	grepTool,
+} from "./grep.js";
+export {
+	createLsTool,
+	type LsOperations,
+	type LsToolDetails,
+	type LsToolInput,
+	type LsToolOptions,
+	lsTool,
+} from "./ls.js";
 export {
 	createReadTool,
 	type ReadOperations,
 	type ReadToolDetails,
+	type ReadToolInput,
 	type ReadToolOptions,
 	readTool,
 } from "./read.js";
@@ -26,7 +56,13 @@ export {
 	truncateLine,
 	truncateTail,
 } from "./truncate.js";
-export { createWriteTool, type WriteOperations, type WriteToolOptions, writeTool } from "./write.js";
+export {
+	createWriteTool,
+	type WriteOperations,
+	type WriteToolInput,
+	type WriteToolOptions,
+	writeTool,
+} from "./write.js";
 
 import type { AgentTool } from "@mariozechner/pi-agent-core";
 import { type BashToolOptions, bashTool, createBashTool } from "./bash.js";

packages/coding-agent/src/core/tools/ls.ts

@@ -1,5 +1,5 @@
 import type { AgentTool } from "@mariozechner/pi-agent-core";
-import { Type } from "@sinclair/typebox";
+import { type Static, Type } from "@sinclair/typebox";
 import { existsSync, readdirSync, statSync } from "fs";
 import nodePath from "path";
 import { resolveToCwd } from "./path-utils.js";
@@ -10,6 +10,8 @@ const lsSchema = Type.Object({
 	limit: Type.Optional(Type.Number({ description: "Maximum number of entries to return (default: 500)" })),
 });
 
+export type LsToolInput = Static<typeof lsSchema>;
+
 const DEFAULT_LIMIT = 500;
 
 export interface LsToolDetails {

packages/coding-agent/src/core/tools/read.ts

@@ -1,6 +1,6 @@
 import type { AgentTool } from "@mariozechner/pi-agent-core";
 import type { ImageContent, TextContent } from "@mariozechner/pi-ai";
-import { Type } from "@sinclair/typebox";
+import { type Static, Type } from "@sinclair/typebox";
 import { constants } from "fs";
 import { access as fsAccess, readFile as fsReadFile } from "fs/promises";
 import { formatDimensionNote, resizeImage } from "../../utils/image-resize.js";
@@ -14,6 +14,8 @@ const readSchema = Type.Object({
 	limit: Type.Optional(Type.Number({ description: "Maximum number of lines to read" })),
 });
 
+export type ReadToolInput = Static<typeof readSchema>;
+
 export interface ReadToolDetails {
 	truncation?: TruncationResult;
 }

packages/coding-agent/src/core/tools/write.ts

@@ -1,5 +1,5 @@
 import type { AgentTool } from "@mariozechner/pi-agent-core";
-import { Type } from "@sinclair/typebox";
+import { type Static, Type } from "@sinclair/typebox";
 import { mkdir as fsMkdir, writeFile as fsWriteFile } from "fs/promises";
 import { dirname } from "path";
 import { resolveToCwd } from "./path-utils.js";
@@ -9,6 +9,8 @@ const writeSchema = Type.Object({
 	content: Type.String({ description: "Content to write to the file" }),
 });
 
+export type WriteToolInput = Static<typeof writeSchema>;
+
 /**
  * Pluggable operations for the write tool.
  * Override these to delegate file writing to remote systems (e.g., SSH).

packages/coding-agent/src/index.ts

@@ -46,10 +46,13 @@ export type {
 	AgentToolResult,
 	AgentToolUpdateCallback,
 	AppAction,
+	BashToolCallEvent,
 	BeforeAgentStartEvent,
 	CompactOptions,
 	ContextEvent,
 	ContextUsage,
+	CustomToolCallEvent,
+	EditToolCallEvent,
 	ExecOptions,
 	ExecResult,
 	Extension,
@@ -69,15 +72,19 @@ export type {
 	ExtensionUIContext,
 	ExtensionUIDialogOptions,
 	ExtensionWidgetOptions,
+	FindToolCallEvent,
+	GrepToolCallEvent,
 	InputEvent,
 	InputEventResult,
 	InputSource,
 	KeybindingsManager,
 	LoadExtensionsResult,
+	LsToolCallEvent,
 	MessageRenderer,
 	MessageRenderOptions,
 	ProviderConfig,
 	ProviderModelConfig,
+	ReadToolCallEvent,
 	RegisteredCommand,
 	RegisteredTool,
 	SessionBeforeCompactEvent,
@@ -100,6 +107,7 @@ export type {
 	UserBashEvent,
 	UserBashEventResult,
 	WidgetPlacement,
+	WriteToolCallEvent,
 } from "./core/extensions/index.js";
 export {
 	createExtensionRuntime,
@@ -111,6 +119,7 @@ export {
 	isGrepToolResult,
 	isLsToolResult,
 	isReadToolResult,
+	isToolCallEventType,
 	isWriteToolResult,
 	wrapRegisteredTool,
 	wrapRegisteredTools,
@@ -196,6 +205,7 @@ export {
 export {
 	type BashOperations,
 	type BashToolDetails,
+	type BashToolInput,
 	type BashToolOptions,
 	bashTool,
 	codingTools,
@@ -203,23 +213,28 @@ export {
 	DEFAULT_MAX_LINES,
 	type EditOperations,
 	type EditToolDetails,
+	type EditToolInput,
 	type EditToolOptions,
 	editTool,
 	type FindOperations,
 	type FindToolDetails,
+	type FindToolInput,
 	type FindToolOptions,
 	findTool,
 	formatSize,
 	type GrepOperations,
 	type GrepToolDetails,
+	type GrepToolInput,
 	type GrepToolOptions,
 	grepTool,
 	type LsOperations,
 	type LsToolDetails,
+	type LsToolInput,
 	type LsToolOptions,
 	lsTool,
 	type ReadOperations,
 	type ReadToolDetails,
+	type ReadToolInput,
 	type ReadToolOptions,
 	readTool,
 	type ToolsOptions,
@@ -229,6 +244,7 @@ export {
 	truncateLine,
 	truncateTail,
 	type WriteOperations,
+	type WriteToolInput,
 	type WriteToolOptions,
 	writeTool,
 } from "./core/tools/index.js";