ComposioHQ/composio · error · ResponseTooLargeError

File size ({content_length} bytes) exceeds maximum allowed s

Error message

File size ({content_length} bytes) exceeds maximum allowed size ({max_size} bytes)

What it means

MCPServer.create wraps any unexpected exception from the underlying MCP server creation API call into a generic ValidationError('Failed to create MCP server'). The original cause is chained via `from e`, so inspect __cause__ to find the real problem (auth, network, invalid toolkit slug, backend error).

Source

Thrown at python/composio/core/models/_files.py:444

            f"Please provide a direct URL to the file."
        )

    # Check for successful response
    if not response.ok:
        response.close()
        raise ErrorUploadingFile(
            f"Failed to fetch file from URL: {_sanitize_url_for_logging(url)}. "
            f"Status: {response.status_code}"
        )

    # Check Content-Length header first (early abort for oversized files).
    # The header is a hint from the remote server: `parse_content_length`
    # returns None for anything untrustworthy, and the streaming guard below
    # is the authoritative limit.
    content_length = parse_content_length(response.headers.get("Content-Length"))
    if content_length is not None and content_length > max_size:
        response.close()
        raise ResponseTooLargeError(
            f"File size ({content_length} bytes) exceeds maximum allowed "
            f"size ({max_size} bytes)"
        )

    # Stream response with size tracking
    chunks: t.List[bytes] = []
    total_bytes = 0
    chunk_size = 8192  # 8 KB chunks

    try:
        for chunk in response.iter_content(chunk_size=chunk_size):
            if chunk:
                total_bytes += len(chunk)
                if total_bytes > max_size:
                    response.close()
                    raise ResponseTooLargeError(
                        f"Response size exceeds maximum allowed size ({max_size} bytes)"
                    )

View on GitHub (pinned to 64b1b85502)

Solutions

  1. Inspect exc.__cause__ (or the full traceback) to identify the underlying error
  2. Verify COMPOSIO_API_KEY is set and valid
  3. Confirm each toolkit slug/config is correct and supported for MCP servers
  4. Retry after transient network/backend failures; check Composio status if it persists

Example fix

# before
mcp = server.create(toolkits=['github'])
# after
try:
    mcp = server.create(toolkits=['github'])
except ValidationError as e:
    cause = e.__cause__ or e
    print(f'MCP create failed: {cause}')
    raise
Defensive patterns

Strategy: try-catch

Validate before calling

from composio import Composio
client = Composio()  # raises early if COMPOSIO_API_KEY missing/invalid
valid = ['github', 'slack']  # confirm slugs exist before calling
mcp = server.create(toolkits=valid)

Type guard

def is_supported_toolkit(slug: str, client) -> bool:
    return any(tk.slug == slug or tk.name == slug for tk in client.tools.get_list())

Try / catch

from composio.core.errors import ValidationError
import time

for attempt in range(3):
    try:
        mcp = server.create(toolkits=['github'])
        break
    except ValidationError as e:
        cause = str(e.__cause__ or e)
        if attempt < 2 and ('timeout' in cause.lower() or 'connection' in cause.lower()):
            time.sleep(2 ** attempt)
            continue
        raise RuntimeError(f'MCP server creation failed: {cause}') from e

Prevention

When it happens

Trigger: Any exception raised inside MCPServer.create's try block: invalid API key, unknown toolkit slug, network failure to the Composio backend, malformed MCPToolkitConfig, or a 4xx/5xx response during server creation.

Common situations: Expired or missing COMPOSIO_API_KEY; typo'd toolkit string; transient backend outage; passing config fields the backend rejects.

Related errors

AI-assisted analysis of ComposioHQ/composio@64b1b85502 (2026-08-28). Data as JSON: /api/errors/35ed2a53c9440e67. Report an issue: GitHub.