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

Annotations already declare readOnlyHint, openWorldHint, and non-destructive behavior. The description adds useful context by tying the result to an API key and naming the endpoint and returned identity fields; it does not cover rate limits or error behavior, but those are minor for this zero-param read.

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 compact sentences: it front-loads what the tool returns and follows with the endpoint. Every element — identity scope, return fields, endpoint — earns its place.

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 identity endpoint with no output schema, the description is nearly complete: it names the returned fields and the endpoint. It could say more about response shape or auth failure behavior, but that is not essential here.

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?

There are zero input parameters, so the baseline is 4. The empty schema is appropriate, and the description correctly avoids inventing parameter semantics.

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 states a specific resource and scope: the Zettle user and organization associated with the API key, including the exact endpoint and key return fields. It is clearly distinguishable from siblings such as account balance, payout info, and transaction listing.

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 purpose implies when to use it — identifying the current API key's account — but there is no explicit when-to-use/when-not guidance and no named alternatives. An agent can infer the use case from the description, but must reason about siblings itself.

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