mercari_home

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

With no annotations, the description carries the transparency burden. It discloses that the tool is 'Credential-free public data' and uses 'an anonymous, login-free session', which effectively tells the agent no authentication is needed. It also describes the data normalization, though it omits potential rate limits or pagination details.

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?

The description is two sentences, front-loaded with the primary action, and every sentence adds value: first states the purpose, second details the output and auth nature. No redundancy.

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 zero-parameter tool, the description is complete. It names the return fields ('title, price, thumbnail, condition, seller'), specifies the data source (Mercari mobile app API), and notes the credential-free access. No output schema exists, so this textual description fully compensates.

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?

The tool has zero parameters, so schema coverage is trivially 100%. The description does not need to explain parameter meaning; it focuses on the output. The baseline for 0 params is 4, and the description appropriately does not invent parameter guidance.

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?

The description clearly identifies the tool as 'Get Mercari home feed' and explains it returns 'Mercari's own curated home-feed recommendations', which is specific and distinct from siblings like mercari_search or mercari_item. It names the resource and the result.

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 implies usage for fetching a general recommended feed ('curated home-feed recommendations') but does not explicitly state when to use this versus search or item lookup, nor any exclusions. No alternative tools are named.

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