FlowiseAI/Flowise · error · Error

Values must be a valid JSON array

Error message

Values must be a valid JSON array

What it means

Thrown inside UpdateValuesTool._call when JSON.parse(params.values) throws. The UpdateValuesSchema declares values as a string that must itself be valid JSON (e.g. "[[\"A1\",\"B1\"]]"), because the tool serializes the parsed array into the Google Sheets values body. The inner try/catch converts any parse failure — SyntaxError from a trailing comma, unquoted key, or a raw non-JSON string — into this fixed message, discarding the original parse error.

Source

Thrown at packages/components/nodes/tools/GoogleSheets/core.ts:390

            method: 'PUT',
            headers: {}
        }
        super({
            ...toolInput,
            accessToken: args.accessToken
        })
        this.defaultParams = args.defaultParams || {}
    }

    async _call(arg: any): Promise<string> {
        const params = { ...arg, ...this.defaultParams }

        try {
            let values
            try {
                values = JSON.parse(params.values)
            } catch (error) {
                throw new Error('Values must be a valid JSON array')
            }

            const body = {
                values,
                majorDimension: params.majorDimension || 'ROWS'
            }

            const queryParams = new URLSearchParams()
            queryParams.append('valueInputOption', params.valueInputOption || 'USER_ENTERED')

            const encodedRange = encodeURIComponent(params.range)
            const endpoint = `spreadsheets/${params.spreadsheetId}/values/${encodedRange}?${queryParams.toString()}`

            return await this.makeGoogleSheetsRequest({
                endpoint,
                method: 'PUT',
                body,
                params

View on GitHub (pinned to abe4a8601a)

Solutions

1. Pre-stringify the array exactly once before assigning to values: values: JSON.stringify([["A1","B1"]]).
2. Validate with JSON.parse in a guard before invoking the tool so you get the real parse error position.
3. If the source is an agent, tighten the schema description or add a few-shot example showing the double-bracket string shape.
4. Confirm defaultParams.values is not simultaneously set to a different shape than arg.values (the spread { ...arg, ...this.defaultParams } lets defaults clobber a good arg).

Example fix

// before — values is a CSV-like string, parse fails
const res = await updateValues.invoke({ spreadsheetId, range: 'A1:B1', values: 'a,b' })
// after — values is a JSON-stringified 2D array
const res = await updateValues.invoke({ spreadsheetId, range: 'A1:B1', values: JSON.stringify([['a','b']]) })

function asValues2D(input: unknown): string {
  // accept array, JSON string of array, or fail fast with a clear error
  let arr: unknown
  if (typeof input === 'string') {
    arr = JSON.parse(input) // throws precise error if bad
  } else {
    arr = input
  }
  if (!Array.isArray(arr) || !arr.every(r => Array.isArray(r))) {
    throw new Error('values must be a 2D array (string[][]), got: ' + JSON.stringify(arr).slice(0,120))
  }
  return JSON.stringify(arr)
}
// then: values: asValues2D(raw)

function is2DStringArray(v: unknown): v is string[][] {
  return Array.isArray(v) && v.every(r => Array.isArray(r) && r.every(c => typeof c === 'string'))
}

try {
  return await updateValues.invoke({ ..., values: asValues2D(raw) })
} catch (e) {
  if (e instanceof Error && e.message === 'Values must be a valid JSON array') {
    return { error: 'malformed values', raw } // feed back to agent
  }
  throw e
}

When it happens

Trigger: An LLM agent supplies params.values as a bare array literal "[[a,b]]" without quotes, as a comma-separated list "a,b,c", as a JS object "{values:[[1]]}", or with smart-quotes/special whitespace. Also triggered when defaultParams.values and arg.values merge into a doubled/corrupted string, or when an upstream node emits the array as "[object Array]".

Common situations: Agent models that emit CSV instead of JSON; a previous node passes a stringified array that gets stringified again (double-encoded "\\\"[[1]]\\\""); copy-paste from a spreadsheet cell that contains a leading apostrophe; locale decimal separators (1,5) leaking into the JSON.

Related errors

• Values must be a valid JSON array of value ranges
• Invalid JSON string: ${error instanceof Error ? error.messag
• chatflowId must be a valid array
• Invalid JSON in executeFlowOverrideConfig: ${parseError.mess
• Invalid input array

AI-assisted analysis of FlowiseAI/Flowise@abe4a8601a (2026-08-12). Data as JSON: /api/errors/eedfa1992eb446d7. Report an issue: GitHub.