Who am I on Vinted

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

Annotations declare readOnlyHint=true and openWorldHint=true, and the description does not contradict them. It adds valuable behavioral context beyond the annotations: specific error codes (NOT_AUTHENTICATED, SESSION_EXPIRED), the return fields, and the agent's limitation ('you cannot log in for them'). This is more than what annotations alone convey.

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 three sentences, each serving a distinct purpose: what it returns, when to use it, and how to handle failures. It is front-loaded with the core function and contains no redundant wording.

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 simple read-only tool with one optional parameter and no output schema, the description covers all essential aspects: return fields, usage context, failure handling, and user instructions. It is sufficiently complete for an agent to invoke the tool correctly and respond to errors appropriately.

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 input schema already provides 100% coverage for the 'country' parameter, including its meaning and default behavior. The description does not add new parameter details beyond what the schema states, so it meets the baseline for high schema coverage without needing to compensate.

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 explicitly states what the tool does: 'Returns the signed-in Vinted account for a storefront' with specific fields (user id, username, item count, reputation). This clearly distinguishes it from sibling tools that handle items, messages, or listings.

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?

Provides explicit when-to-use guidance: 'Use it first to check the session is alive before any seller operation.' Also gives concrete failure handling instructions and tells the agent to direct the user to a login command, which is actionable and context-rich.

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