run_mercari_items

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden, and it does disclose two useful behavioral facts: the operation is a pure read of a single item, and it costs a flat 5 points per successful run, which lets the agent reason about budget. It stops short of covering failure behavior, URL-format tolerance, or rate limits.

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?

One sentence, front-loaded with the action and key input, followed by the payload inventory. The field enumeration is long but each item earns its place because no output schema exists. No filler or marketing language.

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?

There is no output schema, so the exhaustive return-field inventory (price/currency, status, shipping details, seller info) is exactly the right compensation and tells the agent what it will get. Combined with the cost disclosure, the definition is nearly complete for a single-parameter lookup, with only error/edge-case behavior 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?

Schema description coverage is 100% and the single 'item' parameter already documents that it accepts an ID or URL with an example. The description's 'by id or URL' simply restates the schema, adding no format detail, so the baseline 3 for high-coverage schemas 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?

States a specific verb and resource ('Get a Mercari (Japan) item by id or URL'), and the 'by id or URL' qualifier implicitly separates it from the sibling run_mercari_items_search. It is clear and unambiguous, but it never names the search sibling explicitly, so differentiation is inferred rather than stated.

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 only implied: the agent can infer it should call this when it already holds an item ID or URL rather than a query string. There is no explicit when-to-use statement, no exclusion of the search path, and no note about what happens with a malformed or non-existent ID.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.