Search live Mercari resale listings by keyword to get listing summaries, prices, thumbnails, conditions, sellers, and total match counts in JSON.
Search Mercari listings. Searches Mercari's live resale marketplace by free-text keyword, returning listing summaries (title, price, thumbnail, condition, seller) plus the total matching count.
| Name | Required | Description | Default |
|---|---|---|---|
| query | Yes | Free-text keyword search |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden. It usefully discloses the return shape (title, price, thumbnail, condition, seller plus total match count), but says nothing about pagination, result limits, rate limits, or whether unauthenticated access works. It adds real value on output but leaves operational behavior opaque.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two tight sentences with zero waste. The core action and scope are front-loaded, and the result-contents clause adds information rather than filler.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a one-parameter search tool with no output schema and no annotations, the description supplies the key missing piece: what the response contains. It omits pagination and result-count limits, which is a minor gap given the tool's simplicity.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100% for the single query parameter, so the schema already documents free-text keyword input. The description repeats that it is a free-text keyword search but adds no syntax, matching rules, or example queries beyond the schema. Baseline 3 is appropriate when the schema does the heavy lifting.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb (search) and resource (Mercari listings) and adds scope details: live resale marketplace, free-text keyword, listing-summary results. An agent can tell it apart from mercari_item (single item) and mercari_autocomplete (suggestions), but the description never names or contrasts those siblings explicitly.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Usage is implied by the verb-plus-keyword framing, which is the obvious entry point for browsing the marketplace, but there is no when-to-use/when-not guidance and no mention of when to prefer mercari_item, mercari_home, or mercari_autocomplete instead.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.