What causes "Expected a TOML array for MCP args" in upstash/context7?

Change the value to a TOML array of strings: args = ["--flag", "--other"]

upstash/context7 · error · Error

Expected a TOML array for MCP args

Error message

Expected a TOML array for MCP args

What it means

The parser found the server's args key but the value does not start with '[' — it expected a TOML array. This happens when args is a plain string, a number, or the '=' is followed by something else.

Source

Thrown at packages/cli/src/setup/toml-editor.ts:86

  }
  throw new Error("Unterminated TOML basic string in MCP args");
}

function parseTomlLiteralString(source: string, start: number): TomlStringToken {
  const endQuote = source.indexOf("'", start + 1);
  if (endQuote === -1) throw new Error("Unterminated TOML literal string in MCP args");
  const value = source.slice(start + 1, endQuote);
  if (value.includes("\n") || value.includes("\r")) {
    throw new Error("Multiline strings are not supported in MCP args");
  }
  return { value, start, end: endQuote + 1 };
}

function parseTomlStringArray(
  source: string,
  start: number
): { tokens: TomlStringToken[]; end: number } {
  if (source[start] !== "[") throw new Error("Expected a TOML array for MCP args");

  const tokens: TomlStringToken[] = [];
  let index = start + 1;
  while (index < source.length) {
    index = skipTomlArrayTrivia(source, index);
    if (source[index] === "]") return { tokens, end: index + 1 };

    const quote = source[index];
    if (quote !== '"' && quote !== "'") {
      throw new Error("MCP args must be a TOML array containing only strings");
    }
    if (source.slice(index, index + 3) === quote.repeat(3)) {
      throw new Error("Multiline strings are not supported in MCP args");
    }

    const token =
      quote === '"' ? parseTomlBasicString(source, index) : parseTomlLiteralString(source, index);
    tokens.push(token);

View on GitHub (pinned to edc9eeb77b)

Solutions

Change the value to a TOML array of strings: args = ["--flag", "--other"]
Ensure nothing (comments excepted) sits between = and [
Reload/re-run the setup command after fixing

Example fix

// before
args = "--api-key ABC"
// after
args = ["--api-key", "ABC"]

Defensive patterns

Strategy: validation

Validate before calling

const m = body.match(/^args\\s*=\\s*(.)/m);
if (!m || m[1] !== '[') throw new Error('args must be an array');

Type guard

function argsValueStartsArray(raw: string): boolean {
  const m = raw.match(/args\\s*=\\s*\\S/);
  return !!m && m[0].endsWith('[');
}

Try / catch

catch (e) { if (/Expected a TOML array/.test(e.message)) { /* rewrite args as an array of strings */ } throw e; }

Prevention

Always define args as an array of quoted strings
Validate config with the target tool before running setup

When it happens

Trigger: args = "--flag --other" (string instead of array) or args = 42 in the MCP server's TOML table.

Common situations: Converting an inline command string to a server entry; copy-pasting from docs that use string form; leftover placeholder values.

Related errors

AI-assisted analysis of upstash/context7@edc9eeb77b (2026-08-28). Data as JSON: /api/errors/aa70772a46e7c66c. Report an issue: GitHub.