Fetch complete Mercari listing details by ID, including description, photos, price, condition, category, hashtags, shipping origin, and similar items.
Get Mercari item detail. Returns a Mercari item-detail page: description, all photos, price, condition, category, hashtags, the shipping origin state, and a "similar items" carousel of related listings.
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | Mercari item id, e.g. from a search result's id field |
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 behavioral burden. It devotes real content to the response payload (description, photos, price, condition, category, hashtags, shipping origin, similar-items carousel), which is useful given there is no output schema. However, it does not explicitly state that the call is read-only or describe auth/rate-limit behavior; 'Get' implies a safe read but nothing more.
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 sentences with the action front-loaded and the payload enumerated afterward. The return-value list is somewhat long but earns its place since no output schema exists to describe the response.
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 detail-fetch tool with no output schema, the description does the heavy lifting by enumerating the returned fields, which is what an agent needs to decide whether this tool supplies the data it wants. It is nearly complete; only read-only/auth context is missing.
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?
With 100% schema coverage on a single required parameter, the schema already documents the id fully. The description adds no id-format or example information beyond what the schema provides, so the baseline 3 applies.
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?
Specific verb+resource: 'Get Mercari item detail' clearly states it fetches a single item's detail page, distinct from siblings like mercari_search, mercari_home, and mercari_autocomplete. It stops short of naming those siblings or stating the relationship, but the singular 'item detail' scope is unambiguous.
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?
The description gives no when-to-use/when-not guidance and never mentions alternatives like mercari_search or mercari_master. The only usage hint ('id, e.g. from a search result's id field') lives in the schema, not the description.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.