Strip incompatible JSON Schema keywords from tool schemas

src/services/api/openaiShim.ts

@@ -29,6 +29,7 @@ import {
   resolveCodexApiCredentials,
   resolveProviderRequest,
 } from './providerConfig.js'
+import { stripIncompatibleSchemaKeywords } from '../../utils/schemaSanitizer.js'
 
 // ---------------------------------------------------------------------------
 // Types — minimal subset of Anthropic SDK types we need to produce
@@ -235,11 +236,12 @@ function normalizeSchemaForOpenAI(
   schema: Record<string, unknown>,
   strict = true,
 ): Record<string, unknown> {
-  if (!schema || typeof schema !== 'object' || Array.isArray(schema)) {
-    return (schema ?? {}) as Record<string, unknown>
+  const sanitizedSchema = stripIncompatibleSchemaKeywords(schema)
+  if (!sanitizedSchema || typeof sanitizedSchema !== 'object' || Array.isArray(sanitizedSchema)) {
+    return (sanitizedSchema ?? {}) as Record<string, unknown>
   }
 
-  const record = { ...schema }
+  const record = { ...sanitizedSchema }
 
   if (record.type === 'object' && record.properties) {
     const properties = record.properties as Record<string, Record<string, unknown>>

src/utils/api.test.ts

@@ -0,0 +1,67 @@
+import { expect, test } from 'bun:test'
+import { z } from 'zod/v4'
+import { getEmptyToolPermissionContext, type Tool, type Tools } from '../Tool.js'
+import { toolToAPISchema } from './api.js'
+
+test('toolToAPISchema strips incompatible schema keywords from input_schema', async () => {
+  const schema = await toolToAPISchema(
+    {
+      name: 'WebFetch',
+      inputSchema: z.strictObject({}),
+      inputJSONSchema: {
+        type: 'object',
+        properties: {
+          url: {
+            type: 'string',
+            format: 'uri',
+            description: 'Public HTTP or HTTPS URL',
+          },
+          metadata: {
+            type: 'object',
+            properties: {
+              callback: {
+                type: 'string',
+                format: 'uri-reference',
+              },
+            },
+          },
+        },
+      },
+      prompt: async () => 'Fetch a URL',
+    } as unknown as Tool,
+    {
+      getToolPermissionContext: async () => getEmptyToolPermissionContext(),
+      tools: [] as unknown as Tools,
+      agents: [],
+    },
+  )
+
+  expect(schema).toMatchObject({
+    input_schema: {
+      type: 'object',
+      properties: {
+        url: {
+          type: 'string',
+          description: 'Public HTTP or HTTPS URL',
+        },
+        metadata: {
+          type: 'object',
+          properties: {
+            callback: {
+              type: 'string',
+            },
+          },
+        },
+      },
+    },
+  })
+
+  const inputSchema = (schema as { input_schema: Record<string, unknown> }).input_schema
+  const properties = inputSchema.properties as Record<string, Record<string, unknown>>
+  expect(properties.url?.format).toBeUndefined()
+  expect(
+    (
+      properties.metadata?.properties as Record<string, Record<string, unknown>>
+    )?.callback?.format,
+  ).toBeUndefined()
+})

src/utils/api.ts

@@ -60,6 +60,7 @@ import {
 import { getPlatform } from './platform.js'
 import { countFilesRoundedRg } from './ripgrep.js'
 import { jsonStringify } from './slowOperations.js'
+import { stripIncompatibleSchemaKeywords } from './schemaSanitizer.js'
 import type { SystemPrompt } from './systemPromptType.js'
 import { getToolSchemaCache } from './toolSchemaCache.js'
 import { windowsPathToPosixPath } from './windowsPaths.js'
@@ -165,6 +166,7 @@ export async function toolToAPISchema(
     if (!isAgentSwarmsEnabled()) {
       input_schema = filterSwarmFieldsFromSchema(tool.name, input_schema)
     }
+    input_schema = stripIncompatibleSchemaKeywords(input_schema)
 
     base = {
       name: tool.name,

src/utils/schemaSanitizer.ts

@@ -0,0 +1,30 @@
+/**
+ * Anthropic-compatible tool schemas reject several JSON Schema keywords that
+ * Zod commonly emits, especially string `format` validators like `uri`.
+ * Strip those fields recursively before sending tool schemas to providers.
+ */
+export function stripIncompatibleSchemaKeywords<T>(
+  schema: T,
+): T {
+  if (Array.isArray(schema)) {
+    return schema.map(item => stripIncompatibleSchemaKeywords(item)) as T
+  }
+
+  if (!schema || typeof schema !== 'object') {
+    return schema
+  }
+
+  const result: Record<string, unknown> = {}
+  for (const [key, value] of Object.entries(schema as Record<string, unknown>)) {
+    if (key === '$schema' || key === 'format' || key === 'propertyNames') {
+      continue
+    }
+
+    result[key] =
+      value && typeof value === 'object'
+        ? stripIncompatibleSchemaKeywords(value)
+        : value
+  }
+
+  return result as T
+}