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

Annotations already establish read-only, idempotent, closed-world behavior, so the description's extra burden is low. It earns credit for disclosing a non-obvious runtime trait — that sign-in is not enabled and the call yields no customer record — which an agent could not learn from the annotations or empty schema.

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 short sentences, front-loaded with the nominal purpose followed by the caveat. Slight overlap between "sign-in is not enabled" and "returns no customer record," but both carry distinct information.

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, closed-world read with no output schema, the description covers what the agent needs: what it nominally does and that it will not return data in this build. It does not specify the shape of the (empty) response, but that is a minor gap given the tool's simplicity.

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 takes zero parameters and schema coverage is 100%, so the baseline is 4. The description correctly adds nothing about parameters because there is nothing to configure.

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?

"Reports the signed-in customer" gives a specific verb and resource, and the second sentence immediately scopes the expectation: this build returns no record. No sibling in the list covers the same concept, so there is nothing to differentiate against, which is the only reason it falls short of a 5.

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?

There is no explicit when-to-use or alternative named, but the caveat that sign-in is disabled and no customer record is returned effectively signals the agent should not depend on this call for identity. The guidance is implied through the limitation rather than stated as usage policy.

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