ComposioHQ/composio · error · ValidationError

{context}: slug must not start with "COMPOSIO_" — this prefi

Error message

{context}: slug must not start with "COMPOSIO_" — this prefix is reserved for Composio meta tools.

What it means

Raised when a custom tool or toolkit slug starts with COMPOSIO_ (case-insensitive). This prefix is reserved for Composio's meta tools (framework-provided built-ins), so user slugs cannot claim it.

Source

Thrown at python/composio/core/models/custom_tool.py:99

def _validate_slug(slug: str, context: str) -> str:
    """Validate a custom tool or toolkit slug."""
    if not slug:
        raise ValidationError(f"{context}: slug is required")

    if not SLUG_REGEX.match(slug):
        raise ValidationError(
            f"{context}: slug must only contain alphanumeric characters, "
            f"underscores, and hyphens"
        )

    upper = slug.upper()
    if upper.startswith("LOCAL_"):
        raise ValidationError(
            f'{context}: slug must not start with "LOCAL_" — '
            f"this prefix is reserved for internal routing."
        )
    if upper.startswith("COMPOSIO_"):
        raise ValidationError(
            f'{context}: slug must not start with "COMPOSIO_" — '
            f"this prefix is reserved for Composio meta tools."
        )

    return slug


def _compute_final_slug_length(tool_slug: str, toolkit_slug: t.Optional[str]) -> int:
    """Compute the final slug length: LOCAL_[TOOLKIT_]SLUG."""
    length = len(LOCAL_TOOL_PREFIX) + len(tool_slug)
    if toolkit_slug:
        length += len(toolkit_slug) + 1  # +1 for underscore separator
    return length


def _validate_slug_length(
    tool_slug: str, toolkit_slug: t.Optional[str], context: str
) -> None:

View on GitHub (pinned to 64b1b85502)

Solutions

1. Rename the slug to remove the COMPOSIO_ prefix, e.g. 'composio_wrapper' -> 'composio_wrapper_tool' is not enough — use a different namespace like 'wrapper_tool'
2. If wrapping a built-in, name it after the wrapper's purpose, not the vendor

Example fix

# before
Tool(slug="composio_proxy", ...)

# after
Tool(slug="proxy", ...)  # or "my_proxy"

def ensure_prefix(slug: str) -> str:
    if slug.upper().startswith(("LOCAL_", "COMPOSIO_")):
        return "usr_" + slug
    return slug

def has_reserved_prefix(slug: str) -> bool:
    return slug.upper().startswith(("LOCAL_", "COMPOSIO_"))

try:
    Tool(slug=slug, ...)
except ValidationError:
    Tool(slug="app_" + slug, ...)

When it happens

Trigger: Naming a custom tool slug like 'composio_search' or 'COMPOSIO_META' when creating a Tool or toolkit.

Common situations: Wrapping a Composio built-in and prefixing the wrapper with composio_ to indicate origin; teams namespace all tools with a company/tool prefix that happens to be composio_.

Related errors

• {context}: slug must not start with "LOCAL_" — this prefix i
• Could not determine a home directory to store the Composio c
• Cache directory {directory} is not writable please provide a
• module {__name__!r} has no attribute {name!r}
• Failed to upload to S3: {_sanitize_url_for_logging(url)}. Er

AI-assisted analysis of ComposioHQ/composio@64b1b85502 (2026-08-28). Data as JSON: /api/errors/906fc77fc91a9c70. Report an issue: GitHub.