fix: handle missing skill parameter in SkillTool (#485)

* fix: handle missing skill parameter in SkillTool

* fix: preserve SkillTool schema contract

* fix: align SkillTool schema error output

src/tools/SkillTool/SkillTool.test.ts

@@ -0,0 +1,31 @@
+import { describe, expect, test } from 'bun:test'
+
+import { SkillTool } from './SkillTool.js'
+
+describe('SkillTool missing parameter handling', () => {
+  test('missing skill stays required at the schema level', async () => {
+    const parsed = SkillTool.inputSchema.safeParse({})
+
+    expect(parsed.success).toBe(false)
+  })
+
+  test('validateInput still returns an actionable error when called with missing skill', async () => {
+    const result = await SkillTool.validateInput?.({} as never, {
+      options: { tools: [] },
+      messages: [],
+    } as never)
+
+    expect(result).toEqual({
+      result: false,
+      message:
+        'Missing skill name. Pass the slash command name as the skill parameter (e.g., skill: "commit" for /commit, skill: "review-pr" for /review-pr).',
+      errorCode: 1,
+    })
+  })
+
+  test('valid skill input still parses and validates', async () => {
+    const parsed = SkillTool.inputSchema.safeParse({ skill: 'commit' })
+
+    expect(parsed.success).toBe(true)
+  })
+})

src/tools/SkillTool/SkillTool.ts

@@ -352,6 +352,16 @@ export const SkillTool: Tool<InputSchema, Output, Progress> = buildTool({
   toAutoClassifierInput: ({ skill }) => skill ?? '',
 
   async validateInput({ skill }, context): Promise<ValidationResult> {
+    if (!skill || typeof skill !== 'string') {
+      return {
+        result: false,
+        message:
+          'Missing skill name. Pass the slash command name as the skill parameter ' +
+          '(e.g., skill: "commit" for /commit, skill: "review-pr" for /review-pr).',
+        errorCode: 1,
+      }
+    }
+
     // Skills are just skill names, no arguments
     const trimmed = skill.trim()
     if (!trimmed) {
@@ -434,7 +444,7 @@ export const SkillTool: Tool<InputSchema, Output, Progress> = buildTool({
     context,
   ): Promise<PermissionDecision> {
     // Skills are just skill names, no arguments
-    const trimmed = skill.trim()
+    const trimmed = skill ?? ''
 
     // Remove leading slash if present (for compatibility)
     const commandName = trimmed.startsWith('/') ? trimmed.substring(1) : trimmed
@@ -592,7 +602,7 @@ export const SkillTool: Tool<InputSchema, Output, Progress> = buildTool({
     // - Skill is a prompt-based skill
 
     // Skills are just names, with optional arguments
-    const trimmed = skill.trim()
+    const trimmed = skill ?? ''
 
     // Remove leading slash if present (for compatibility)
     const commandName = trimmed.startsWith('/') ? trimmed.substring(1) : trimmed