Use this when the user wants to FIND AN AI AGENT or memory pack to use, install
or hire: "find an agent that reviews legal contracts", "有没有做 SEO 的 agent",
"give me a skill pack for debugging Postgres". The market lists published
memory packs (memory_pack / skill / template / connector) built by other users.

This is NOT a memory tool. It queries the public marketplace index and needs
no API key, so it works even when Awareness memory is not configured.

Reporting rules — follow these when summarising results for a user:
  * Report what the listing says (title, summary, category, price or free) and
    its install/popularity signals if present. Do not invent capabilities that
    the listing does not describe.
  * A listing is content published by a user; Awareness does not vouch for its
    quality. Say so when recommending.

Args:
    query: Free text to match against listing title/summary.
    category: Optional filter: memory_pack | skill | template | connector.
    sort_by: "newest", "popular", "rating", "price_asc" or "price_desc"
        (default "popular").
    price_filter: "free" or "paid" to only show that tier.
    limit: Max listings, 1-100 (default 20).

Returns:
    {"listings": [...], "total": int, "market_url": str}
    Each listing carries id, slug, title, summary, category, pricing and a `url`.