fix(ai-chat): model-friendly tool-input validation errors (#190)

When the in-app AI chat issued a parallel batch of tool calls, the model
sometimes dropped a required parameter (typically a repeated `pageId`). zod
rejected it and the AI SDK surfaced the raw zod text
("Invalid input: expected string, received undefined") to the model, which is
not actionable — so it could not reliably retry.

Add a centralized `modelFriendlyInput(shape)` wrapper for in-app tool input
schemas:
- the model-facing JSON schema is derived from the SAME zod shape via
  `z.toJSONSchema(z.object(shape), { target: 'draft-7' })`, so `required`,
  `description` and field constraints are unchanged (contract preserved);
- on a validation failure `validate` returns a human-readable Error naming the
  offending parameter(s) plus a fixed retry hint ("Include every REQUIRED
  parameter ... do not drop ids like pageId"), which the SDK relays to the model
  via InvalidToolInputError;
- on success it returns the parsed (unknown-key-stripped) data, preserving the
  existing strip guardrails (deletePage never forwards permanentlyDelete/
  forceDelete; transformPage never forwards deleteComments).

Applied in ai-chat-tools.service.ts (the sharedTool builder + every inline
tool inputSchema) and in public-share-chat-tools.service.ts. Values are never
guessed and the required/optional contract is untouched.

Tests: new model-friendly-input.spec.ts (friendly message names the param +
hint; unknown keys stripped; JSON schema keeps required/description); the two
.parse()-based guardrail tests reworked to assert via the new validate path.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/server/src/core/ai-chat/tools/ai-chat-tools.service.spec.ts

@@ -120,21 +120,26 @@ describe('AiChatToolsService deletePage guardrail (H4)', () => {
     const tools = await buildTools();
     const deletePage = tools.deletePage;
 
-    // The Zod input schema only allows `pageId`; parsing strips/ignores extra
+    // inputSchema is now an AI SDK `Schema` (not a raw zod object). Its
-    // keys, so a permanent/force flag is never part of the validated input.
+    // `validate` runs the same zod safeParse and forwards the STRIPPED data, so
+    // a permanent/force flag is never part of the validated input the SDK then
+    // hands to execute.
     const schema = (deletePage as unknown as { inputSchema: unknown })
       .inputSchema as {
-      parse: (v: unknown) => Record<string, unknown>;
+      validate: (
+        v: unknown,
+      ) => Promise<{ success: boolean; value?: Record<string, unknown> }>;
     };
-    const parsed = schema.parse({
+    const result = await schema.validate({
       pageId: 'page-789',
       permanentlyDelete: true,
       forceDelete: true,
     });
 
-    expect(parsed).toHaveProperty('pageId', 'page-789');
+    expect(result.success).toBe(true);
-    expect(parsed).not.toHaveProperty('permanentlyDelete');
+    expect(result.value).toHaveProperty('pageId', 'page-789');
-    expect(parsed).not.toHaveProperty('forceDelete');
+    expect(result.value).not.toHaveProperty('permanentlyDelete');
+    expect(result.value).not.toHaveProperty('forceDelete');
   });
 });
 
@@ -207,21 +212,25 @@ describe('AiChatToolsService expanded toolset guardrails', () => {
     const tools = await buildTools();
     const transformPage = tools.transformPage;
 
-    // The Zod input schema only allows pageId/transformJs/dryRun; parsing
+    // inputSchema is now an AI SDK `Schema`; its `validate` runs the same zod
-    // strips unknown keys, so deleteComments can never reach the client.
+    // safeParse, which only allows pageId/transformJs/dryRun and strips unknown
+    // keys — so deleteComments can never reach the client.
     const schema = (transformPage as unknown as { inputSchema: unknown })
       .inputSchema as {
-      parse: (v: unknown) => Record<string, unknown>;
+      validate: (
+        v: unknown,
+      ) => Promise<{ success: boolean; value?: Record<string, unknown> }>;
     };
-    const parsed = schema.parse({
+    const result = await schema.validate({
       pageId: 'p',
       transformJs: '(d)=>d',
       dryRun: true,
       deleteComments: true,
     });
 
-    expect(parsed).toHaveProperty('pageId', 'p');
+    expect(result.success).toBe(true);
-    expect(parsed).not.toHaveProperty('deleteComments');
+    expect(result.value).toHaveProperty('pageId', 'p');
+    expect(result.value).not.toHaveProperty('deleteComments');
   });
 });
 

apps/server/src/core/ai-chat/tools/ai-chat-tools.service.ts

@@ -15,6 +15,7 @@ import {
 } from './docmost-client.loader';
 import { resolveCurrentPageResult } from './current-page.util';
 import { parseNodeArg } from './parse-node-arg';
+import { modelFriendlyInput } from './model-friendly-input';
 
 /**
  * Per-user, per-request adapter that exposes Docmost READ operations to the
@@ -102,9 +103,9 @@ export class AiChatToolsService {
     ): Tool =>
       tool({
         description: spec.description,
-        inputSchema: spec.buildShape
+        inputSchema: modelFriendlyInput(
-          ? z.object(spec.buildShape(z) as z.ZodRawShape)
+          spec.buildShape ? (spec.buildShape(z) as z.ZodRawShape) : {},
-          : z.object({}),
+        ),
         execute,
       });
 
@@ -118,7 +119,7 @@ export class AiChatToolsService {
           'and entities), not a full sentence. If the first results look weak ' +
           'or incomplete, search again with different wording or synonyms ' +
           'before answering.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           query: z.string().describe('The search query.'),
           limit: z
             .number()
@@ -227,7 +228,7 @@ export class AiChatToolsService {
           '"the current page", or "here" refers to. Returns the page id and title, ' +
           'or null if the user is not currently on a page. Call this first whenever ' +
           'the user refers to the current page without giving an explicit id.',
-        inputSchema: z.object({}),
+        inputSchema: modelFriendlyInput({}),
         execute: async () => resolveCurrentPageResult(openedPage),
       }),
 
@@ -235,7 +236,7 @@ export class AiChatToolsService {
         description:
           'Fetch a single page as Markdown by its page id. Returns the page ' +
           'title and its Markdown content.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id (or slugId) of the page.'),
         }),
         execute: async ({ pageId }) => {
@@ -259,7 +260,7 @@ export class AiChatToolsService {
           'Create a new page with a Markdown body in a space, optionally under ' +
           'a parent page. Returns the new page id and title. Reversible: a page ' +
           'can be moved to trash later.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           title: z.string().describe('The title of the new page.'),
           content: z
             .string()
@@ -294,7 +295,7 @@ export class AiChatToolsService {
         description:
           "Replace a page's body with new Markdown content (and optionally its " +
           'title). Reversible: the previous version is kept in page history.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page to update.'),
           content: z.string().describe('The new page body as Markdown.'),
           title: z
@@ -316,7 +317,7 @@ export class AiChatToolsService {
         description:
           "Rename a page (change its title only; the body is untouched). " +
           'Reversible: rename back at any time.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page to rename.'),
           title: z.string().describe('The new title.'),
         }),
@@ -331,7 +332,7 @@ export class AiChatToolsService {
         description:
           'Move a page under a new parent page, or to the space root when no ' +
           'parent is given. Reversible: move it back at any time.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page to move.'),
           parentPageId: z
             .string()
@@ -353,7 +354,7 @@ export class AiChatToolsService {
         description:
           'Move a page to the trash (SOFT delete only — fully reversible; the ' +
           'page can be restored from trash). This NEVER permanently deletes.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page to move to trash.'),
         }),
         // GUARDRAIL (§14 H4): the only field ever passed to the client is
@@ -379,7 +380,7 @@ export class AiChatToolsService {
           '"selection not found" error, retry with a corrected EXACT selection ' +
           'copied verbatim from a single paragraph/block. Reversible via the ' +
           'comment UI.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page to comment on.'),
           content: z.string().describe('The comment body as Markdown.'),
           selection: z
@@ -428,7 +429,7 @@ export class AiChatToolsService {
         description:
           'Resolve or reopen a top-level comment thread (reversible — toggle ' +
           'the resolved flag). Only top-level comments can be resolved.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           commentId: z
             .string()
             .describe('The id of the top-level comment to resolve/reopen.'),
@@ -460,7 +461,7 @@ export class AiChatToolsService {
           'List the most recent pages, optionally scoped to a single space. ' +
           'Returns a bounded list (default 50, max 100). Pass tree:true (with ' +
           "spaceId) to instead get the space's full page hierarchy as a nested tree.",
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           spaceId: z
             .string()
             .optional()
@@ -488,7 +489,7 @@ export class AiChatToolsService {
           'List sidebar pages for a space. With no pageId, returns the ' +
           "space's ROOT pages; with a pageId, returns that page's direct " +
           'CHILDREN.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           spaceId: z.string().describe('The id of the space.'),
           pageId: z
             .string()
@@ -520,7 +521,7 @@ export class AiChatToolsService {
         description:
           'Read a table as a matrix of cell texts (plus a parallel cellIds ' +
           'matrix so cells can be addressed for rich edits).',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page.'),
           tableRef: z
             .string()
@@ -536,7 +537,7 @@ export class AiChatToolsService {
       listComments: tool({
         description:
           'List all comments on a page (content as Markdown).',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page.'),
         }),
         execute: async ({ pageId }) => await client.listComments(pageId),
@@ -544,7 +545,7 @@ export class AiChatToolsService {
 
       getComment: tool({
         description: 'Fetch a single comment by id (content as Markdown).',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           commentId: z.string().describe('The id of the comment.'),
         }),
         execute: async ({ commentId }) => await client.getComment(commentId),
@@ -554,7 +555,7 @@ export class AiChatToolsService {
         description:
           'Find new comments across a space (optionally scoped to a subtree) ' +
           'created after a given timestamp.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           spaceId: z.string().describe('The id of the space to scan.'),
           since: z
             .string()
@@ -586,7 +587,7 @@ export class AiChatToolsService {
         description:
           'Fetch a single page-history version including its lossless ' +
           'ProseMirror content.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           historyId: z.string().describe('The id of the history version.'),
         }),
         execute: async ({ historyId }) =>
@@ -604,7 +605,7 @@ export class AiChatToolsService {
           'Export a page to a single self-contained Docmost-flavoured ' +
           'Markdown file (meta + body + comment threads). Lossless round-trip ' +
           'with importPageMarkdown.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page to export.'),
         }),
         execute: async ({ pageId }) => {
@@ -630,7 +631,7 @@ export class AiChatToolsService {
           '{"type":"text","text":"x","marks":[{"type":"bold"}]}. The node arg ' +
           'may be a JSON object or a JSON string (both accepted). Reversible: ' +
           'the previous version is kept in page history.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page.'),
           nodeId: z
             .string()
@@ -663,7 +664,7 @@ export class AiChatToolsService {
           '{"type":"text","text":"x","marks":[{"type":"bold"}]}. The node arg ' +
           'may be a JSON object or a JSON string (both accepted). Reversible ' +
           'via page history.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page.'),
           node: z
             .any()
@@ -722,7 +723,7 @@ export class AiChatToolsService {
           'object or a JSON string (both accepted). Omit content for a ' +
           'title-only update. Reversible: the previous version is kept in page ' +
           'history.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page to update.'),
           content: z
             .any()
@@ -753,7 +754,7 @@ export class AiChatToolsService {
         description:
           'Insert a row of plain-text cells into a table. Reversible via ' +
           'page history.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page.'),
           tableRef: z
             .string()
@@ -772,7 +773,7 @@ export class AiChatToolsService {
       tableDeleteRow: tool({
         description:
           'Delete a table row at a 0-based index. Reversible via page history.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page.'),
           tableRef: z
             .string()
@@ -787,7 +788,7 @@ export class AiChatToolsService {
         description:
           'Set the plain-text content of a table cell at [row, col] (0-based). ' +
           'Reversible via page history.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page.'),
           tableRef: z
             .string()
@@ -817,7 +818,7 @@ export class AiChatToolsService {
           'Make a page PUBLICLY accessible and return its public URL. ' +
           'Reversible via unsharePage. Only share when the user explicitly ' +
           'asked, since this exposes the page to anyone with the link.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page to share.'),
           searchIndexing: z
             .boolean()
@@ -844,7 +845,7 @@ export class AiChatToolsService {
           "page's ProseMirror document for complex/scripted rewrites. dryRun " +
           '(default true) previews a diff WITHOUT writing; set dryRun:false to ' +
           'apply. Reversible: applying creates a new page-history snapshot.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z.string().describe('The id of the page to transform.'),
           transformJs: z
             .string()

apps/server/src/core/ai-chat/tools/model-friendly-input.spec.ts

@@ -0,0 +1,89 @@
+import { z } from 'zod';
+import { modelFriendlyInput } from './model-friendly-input';
+
+/**
+ * Unit tests for the model-friendly input wrapper (issue #190): validation
+ * failures must report a human-readable, parameter-naming message (not the raw
+ * zod text), successful validation must strip unknown keys (preserving the
+ * strip guardrails), and the JSON schema handed to the model must keep the
+ * required/optional contract and field descriptions intact.
+ */
+describe('modelFriendlyInput', () => {
+  // A representative shape: a required id + description, plus an optional field.
+  const shape = {
+    pageId: z.string().describe('The id of the page to comment on.'),
+    content: z.string(),
+    limit: z.number().int().optional(),
+  };
+
+  // The AI SDK `Schema` exposes a `validate` callback and a `jsonSchema` field;
+  // type them loosely for the test.
+  type SchemaLike = {
+    validate?: (
+      v: unknown,
+    ) =>
+      | { success: boolean; value?: Record<string, unknown>; error?: Error }
+      | PromiseLike<{
+          success: boolean;
+          value?: Record<string, unknown>;
+          error?: Error;
+        }>;
+    jsonSchema: unknown;
+  };
+
+  it('reports a model-friendly error naming the missing REQUIRED param + retry hint', async () => {
+    const schema = modelFriendlyInput(shape) as unknown as SchemaLike;
+    // Drop the required `pageId` (the parallel-batch failure mode).
+    const result = await schema.validate!({ content: 'hi' });
+
+    expect(result.success).toBe(false);
+    const message = result.error?.message ?? '';
+    // Names the offending parameter by name.
+    expect(message).toContain('pageId');
+    // Carries the fixed actionable retry hint.
+    expect(message).toContain('Include every REQUIRED parameter and retry');
+    expect(message).toContain('do not drop ids like "pageId"');
+    // It must NOT be the bare raw zod text alone — our wrapper prefix is present.
+    expect(message).toContain('Invalid tool input');
+  });
+
+  it('accepts valid input and STRIPS unknown keys (keeps declared ones)', async () => {
+    const schema = modelFriendlyInput(shape) as unknown as SchemaLike;
+    const result = await schema.validate!({
+      pageId: 'p-1',
+      content: 'hello',
+      // An extra unknown key a (compromised) model might emit.
+      permanentlyDelete: true,
+    });
+
+    expect(result.success).toBe(true);
+    expect(result.value).toEqual({ pageId: 'p-1', content: 'hello' });
+    expect(result.value).not.toHaveProperty('permanentlyDelete');
+  });
+
+  it('produces a draft-07 JSON schema that preserves required + descriptions', async () => {
+    const schema = modelFriendlyInput(shape) as unknown as SchemaLike;
+    // jsonSchema may be a value or a promise; await either way.
+    const json = (await Promise.resolve(schema.jsonSchema)) as {
+      required?: string[];
+      properties?: Record<string, { description?: string }>;
+    };
+
+    // Required contract preserved: pageId + content required, limit optional.
+    expect(json.required).toEqual(expect.arrayContaining(['pageId', 'content']));
+    expect(json.required).not.toContain('limit');
+    // Field description preserved.
+    expect(json.properties?.pageId?.description).toBe(
+      'The id of the page to comment on.',
+    );
+  });
+
+  it('handles a root-level type error with a "(root)" parameter name', async () => {
+    const schema = modelFriendlyInput(shape) as unknown as SchemaLike;
+    // Passing a non-object yields an issue with an empty path.
+    const result = await schema.validate!('not an object');
+
+    expect(result.success).toBe(false);
+    expect(result.error?.message).toContain('(root)');
+  });
+});

apps/server/src/core/ai-chat/tools/model-friendly-input.ts

@@ -0,0 +1,72 @@
+import { jsonSchema, type JSONSchema7, type Schema } from 'ai';
+import { z } from 'zod';
+
+// Centralized input-schema wrapper for in-app AI tools. The JSON schema handed
+// to the model is derived from the same zod shape (so `required`/`description`/
+// constraints are unchanged), but validation failures are reported with a
+// human-readable message that NAMES the offending parameter(s) and asks the
+// model to retry with every required field — instead of the raw zod text. This
+// matters for parallel tool-call batches where the model tends to drop a
+// repeated id like `pageId`.
+
+// Fixed, actionable hint appended to every validation error. Kept as a constant
+// so the message stays deterministic and the spec can assert on it verbatim.
+const RETRY_HINT =
+  'Include every REQUIRED parameter and retry; when issuing parallel tool ' +
+  'calls, do not drop ids like "pageId".';
+
+/**
+ * Turn a zod validation error into a concise, model-friendly message that names
+ * each offending parameter (by its dotted path; the root object is "(root)"),
+ * gives a short reason, and ends with the fixed retry hint. Repeated parameter
+ * names are de-duplicated and the output is deterministic.
+ */
+export function formatIssues(error: z.ZodError): string {
+  const seen = new Set<string>();
+  const parts: string[] = [];
+  for (const issue of error.issues) {
+    const name =
+      Array.isArray(issue.path) && issue.path.length > 0
+        ? issue.path.join('.')
+        : '(root)';
+    if (seen.has(name)) continue;
+    seen.add(name);
+    // Prefer zod's own message (e.g. "Invalid input: expected string, received
+    // undefined"); fall back to a generic reason when it is missing.
+    const reason = issue.message ? issue.message : 'missing or invalid';
+    parts.push(`parameter "${name}": ${reason}`);
+  }
+  const summary = parts.length > 0 ? parts.join('; ') : 'invalid tool input';
+  return `Invalid tool input — ${summary}. ${RETRY_HINT}`;
+}
+
+/**
+ * Build an AI SDK `Schema` from a zod raw shape. The JSON schema exposed to the
+ * model is derived from the zod object (preserving `required`, `description`,
+ * and field constraints), so the required/optional contract is UNCHANGED. On a
+ * validation failure we return a model-friendly error (see `formatIssues`); on
+ * success we return the PARSED data, which has unknown keys stripped by zod —
+ * this preserves the existing strip guardrails (e.g. deletePage never forwards
+ * permanentlyDelete/forceDelete; transformPage never forwards deleteComments).
+ */
+export function modelFriendlyInput<Shape extends z.ZodRawShape>(
+  shape: Shape,
+): Schema<z.infer<z.ZodObject<Shape>>> {
+  const object = z.object(shape);
+  // draft-07 JSON schema for the model (keeps required/description/constraints).
+  const schema = z.toJSONSchema(object, { target: 'draft-7' }) as JSONSchema7;
+  return jsonSchema<z.infer<typeof object>>(schema, {
+    validate: (value: unknown) => {
+      const result = object.safeParse(value);
+      if (result.success) {
+        // Return the PARSED (unknown-key-stripped) data so the SDK forwards a
+        // clean object to execute — preserves the existing strip guardrails.
+        return { success: true as const, value: result.data };
+      }
+      return {
+        success: false as const,
+        error: new Error(formatIssues(result.error)),
+      };
+    },
+  });
+}

apps/server/src/core/ai-chat/tools/public-share-chat-tools.service.ts

@@ -5,6 +5,7 @@ import { ShareService } from '../../share/share.service';
 import { SearchService } from '../../search/search.service';
 import { PageRepo } from '@docmost/db/repos/page/page.repo';
 import { jsonToMarkdown } from '../../../collaboration/collaboration.util';
+import { modelFriendlyInput } from './model-friendly-input';
 
 /**
  * Isolated, READ-ONLY toolset for the ANONYMOUS public-share assistant.
@@ -52,7 +53,7 @@ export class PublicShareChatToolsService {
           '(key terms and entities), not a full sentence. If the first ' +
           'results look weak, search again with different wording before ' +
           'answering. Only pages inside this share are ever returned.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           query: z.string().describe('The search query.'),
           limit: z
             .number()
@@ -87,7 +88,7 @@ export class PublicShareChatToolsService {
           'Markdown, by its page id. Returns the page title and its Markdown ' +
           'content. Only pages inside this share can be read; reading any ' +
           'other page fails.',
-        inputSchema: z.object({
+        inputSchema: modelFriendlyInput({
           pageId: z
             .string()
             .describe('The id (or slugId) of a page within this share.'),
@@ -142,7 +143,7 @@ export class PublicShareChatToolsService {
           'List the pages (titles + ids) that make up THIS published ' +
           'documentation share, so you can orient yourself before reading or ' +
           'searching. Only pages inside this share are listed.',
-        inputSchema: z.object({}),
+        inputSchema: modelFriendlyInput({}),
         execute: async () => {
           // Reuse the same share-tree logic the public /shares/tree route uses:
           // it validates the share + workspace, excludes restricted subtrees,