Summary
defineOpenAPIConnection copies each property's default and example into the model-facing JSON Schema verbatim, even when those values contradict the property's declared type. Models follow the example, produce input that fails the generated zod schema, and the tool call dies.
Real specs do this. Xero's official xero_accounting.yaml has 10 boolean properties whose default and example are quoted strings.
Reproduction
Minimal spec exhibiting the pattern:
export default defineOpenAPIConnection({
baseUrl: "https://api.example.com",
description: "Repro.",
spec: {
openapi: "3.0.3",
info: { title: "Repro", version: "1.0.0" },
paths: {
"/things": {
post: {
operationId: "createThing",
requestBody: {
content: {
"application/json": {
schema: {
type: "object",
properties: {
HasAttachments: {
type: "boolean",
default: "false", // string, contradicts type
example: "false", // string, contradicts type
},
},
},
},
},
},
responses: { "200": { description: "OK" } },
},
},
},
},
});The model reliably emits "HasAttachments": "false" and the call fails:
AI_InvalidToolInputError: Invalid input for tool example__createThing:
AI_TypeValidationError: Type validation failed
path: ["body","HasAttachments"]
"Invalid input: expected boolean, received string"
Real-world case
Xero's spec, pinned at commit 853dc01:
HasAttachments:
description: boolean to indicate if an invoice has an attachment
readOnly: true
type: boolean
default: "false"
example: "false"
Scanning that spec for booleans carrying string default/example:
ApprovedForSending, FromIsReconciled, HasAccount, HasAttachments,
HasErrors, HasValidationErrors, IncludePDF, MarkAsSent, SendCopy,
ToIsReconciled
MarkAsSent, IncludePDF and SendCopy are emailInvoice parameters — a model is meant to set those, so it cannot simply be told to omit them.
This bit us in production on a createInvoices call. Four fields failed at once, all from copied examples.
Where
dist/src/runtime/connections/openapi-schema.js. derefSchema walks every key and recurses:
let a={};
for(let[e,o]of Object.entries(n)) a[e]=derefSchema(t,o,r+1,i);
return normalizeSchemaType(a), normalizeNullable(a), anormalizeSchemaType strips type values that aren't valid JSON Schema types, and normalizeNullable folds nullable into type — so there is already a normalization pass here, it just doesn't look at default or example.
Suggested fix
In that same pass, drop default and example when they don't validate against the node's own type. A schema that contradicts itself is a spec bug, and the annotation is the wrong half to trust — dropping it costs the model nothing, while keeping it actively teaches the wrong type.
readOnly: true properties appearing in request schemas at all is arguably a second, separate issue.
Versions
eve 0.39.0ai 7.0.66- Node 24, deployed on Vercel
Summary
defineOpenAPIConnectioncopies each property'sdefaultandexampleinto the model-facing JSON Schema verbatim, even when those values contradict the property's declaredtype. Models follow the example, produce input that fails the generated zod schema, and the tool call dies.Real specs do this. Xero's official
xero_accounting.yamlhas 10 boolean properties whosedefaultandexampleare quoted strings.Reproduction
Minimal spec exhibiting the pattern:
The model reliably emits
"HasAttachments": "false"and the call fails:Real-world case
Xero's spec, pinned at commit
853dc01:Scanning that spec for booleans carrying string
default/example:MarkAsSent,IncludePDFandSendCopyareemailInvoiceparameters — a model is meant to set those, so it cannot simply be told to omit them.This bit us in production on a
createInvoicescall. Four fields failed at once, all from copied examples.Where
dist/src/runtime/connections/openapi-schema.js.derefSchemawalks every key and recurses:normalizeSchemaTypestripstypevalues that aren't valid JSON Schema types, andnormalizeNullablefoldsnullableintotype— so there is already a normalization pass here, it just doesn't look atdefaultorexample.Suggested fix
In that same pass, drop
defaultandexamplewhen they don't validate against the node's owntype. A schema that contradicts itself is a spec bug, and the annotation is the wrong half to trust — dropping it costs the model nothing, while keeping it actively teaches the wrong type.readOnly: trueproperties appearing in request schemas at all is arguably a second, separate issue.Versions
eve0.39.0ai7.0.66