Tencent/WeKnora · error

failed to marshal schema: %v

Error message

failed to marshal schema: %v

What it means

After generating the schema, GenerateSchema[T] marshals it to JSON bytes. json.Marshal on a generated *jsonschema.Schema should rarely fail, but if it does (unsupported values introduced via custom keywords/extensions or a marshaling bug), the function panics.

Source

Thrown at internal/utils/json.go:31

	if err != nil {
		return ""
	}
	return string(json)
}

// GenerateSchema generates JSON schema for type T and returns it as a map
// This is optimized to avoid unnecessary serialization/deserialization
func GenerateSchema[T any]() json.RawMessage {
	schema, err := jsonschema.For[T](nil)
	if err != nil {
		panic(fmt.Sprintf("failed to generate schema: %v", err))
	}

	// Convert schema to map directly through JSON marshaling
	// This is necessary because the schema object doesn't expose its internal structure
	schemaBytes, err := json.Marshal(schema)
	if err != nil {
		panic(fmt.Sprintf("failed to marshal schema: %v", err))
	}

	return schemaBytes
}

View on GitHub (pinned to 988cbb0330)

Solutions

1. Inspect the schema options/extensions passed to jsonschema.For and remove or fix unmarshalable custom values
2. Update the invopop/jsonschema dependency to a version fixing the marshal error
3. Prefer the returned json.RawMessage path without custom extensions, or build the schema map manually
4. Add a recover in tool initialization to identify which tool's type triggers it

Example fix

// before
schema, err := jsonschema.For[T](opts) // opts contains custom unmarshalable extension
// after
schema, err := jsonschema.For[T](nil) // drop unsupported options

func marshalSchemaSafe(schema *jsonschema.Schema) (b []byte, err error) {
    defer func() { if r := recover(); r != nil { err = fmt.Errorf("schema marshal panic: %v", r) } }()
    return json.Marshal(schema)
}

When it happens

Trigger: json.Marshal(schema) returning an error — practically only when the schema contains values with custom MarshalJSON implementations that error, or corrupt/unsupported structures injected through schema options/extensions passed to jsonschema.For.

Common situations: Passing custom schema options/extensions whose types cannot marshal; a library version regression; embedding types with faulty MarshalJSON into tool input structs.

Related errors

• failed to generate schema: %v
• failed to marshal Exa request: %w
• failed to set FAQ metadata: %w
• marshal credentials: %w
• parse rss credentials: %w

AI-assisted analysis of Tencent/WeKnora@988cbb0330 (2026-09-02). Data as JSON: /api/errors/a19693f49e05ec62. Report an issue: GitHub.