langchain-ai/deepagents · error · MarketplaceError

Marketplace must contain a plugins array

Error message

Marketplace {name} must contain a plugins array

What it means

A valid marketplace manifest must contain a `plugins` key whose value is a JSON array. If `plugins` is missing or is not a list (e.g. a dict or string), MarketplaceError is raised with the marketplace's validated name in the message. Entries inside the array that fail parsing are skipped with warnings rather than raising.

Solutions

1. Change `plugins` to a JSON array of plugin entry objects (or add the key if missing).
2. Check the manifest template/docs for the current schema and update the key name.
3. Re-pull the marketplace repo to restore the canonical manifest.

Example fix

// before
{ "name": "team-corp", "plugins": { "a": "./plugins/a" } }
// after
{ "name": "team-corp", "plugins": [ { "id": "a", "source": "./plugins/a" } ] }

import json

def plugins_is_array(path) -> bool:
    doc = json.loads(path.read_text(encoding="utf-8"))
    plugins = doc.get("plugins") if isinstance(doc, dict) else None
    return isinstance(plugins, list) and all(isinstance(e, dict) for e in plugins)

def has_plugins_array(doc: object) -> TypeGuard[dict]:
    return isinstance(doc, dict) and isinstance(doc.get("plugins"), list)

try:
    mp = load_marketplace(root)
except MarketplaceError as exc:
    if "must contain a plugins array" in str(exc):
        fix_manifest_plugins_key(root)
    raise

When it happens

Trigger: load_marketplace / _load_marketplace_file on a manifest where `plugins` is absent, set to an object `{}`, a string, or any non-list value.

Common situations: Hand-writing a manifest with `plugins: {}` keyed by plugin id; renaming the key (e.g. `plugin` singular); an upstream schema change in the manifest format; truncation dropping the array.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• Marketplace manifest
• External event kind must be one of
• Marketplace URL must return a JSON object
• context must be a JSON object.
• Could not parse embedded resource block. Block expected…

AI-assisted analysis of langchain-ai/deepagents@a1af029e6e (2026-08-29). Data as JSON: /api/errors/b7203b63d4aaa30e. Report an issue: GitHub.

Appendix: source

Thrown at libs/code/deepagents_code/plugins/marketplace.py:822

    try:
        raw = json.loads(manifest_path.read_text(encoding="utf-8"))
    except json.JSONDecodeError as exc:
        msg = f"Invalid JSON syntax in {manifest_path}: {exc}"
        raise MarketplaceError(msg) from exc
    except OSError as exc:
        msg = f"Could not read marketplace manifest {manifest_path}: {exc}"
        raise MarketplaceError(msg) from exc
    if not isinstance(raw, dict):
        msg = f"Marketplace manifest {manifest_path} must be a JSON object"
        raise MarketplaceError(msg)
    try:
        name = _validate_name(raw.get("name"), allow_at=False)
    except ValueError as exc:
        raise MarketplaceError(str(exc)) from exc
    plugins_raw = raw.get("plugins")
    if not isinstance(plugins_raw, list):
        msg = f"Marketplace {name} must contain a plugins array"
        raise MarketplaceError(msg)
    warnings: list[str] = []
    plugins = tuple(
        plugin
        for entry in plugins_raw
        if (plugin := _parse_entry(entry, warnings=warnings)) is not None
    )
    for warning in warnings:
        logger.warning("%s", warning)
    metadata = json_object(raw.get("metadata"))
    return PluginMarketplace(
        name=name,
        root=root,
        manifest_path=manifest_path,
        metadata=metadata,
        plugins=plugins,
        warnings=tuple(warnings),
    )

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