Who is signed in

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds substantive context by disclosing what the call returns (identity fields, scopes, owner flag), which matters because no output schema exists. It does not say what happens when nobody is signed in, whether that yields an error or an empty result, which is the main remaining gap.

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 sentences, both earning their place: the first lists the return content, the second gives the usage condition. The payload is front-loaded with no filler.

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 read tool with no output schema, the description covers the essentials: what is returned and when to call it. The only missing piece is unauthenticated or error behavior, a minor gap given the tool's simplicity and its read-only annotation.

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, so the baseline is 4. The description correctly implies no input is needed, and nothing about parameters is left ambiguous.

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 (the signed-in person) and names the fields returned: id, name, email, scopes, and store-owner status. It is clearly distinct from every sibling tool, which handle shelves, products, notes, and downloads. It stops short of a leading verb, but the intent is unambiguous.

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 gives an explicit trigger: 'Call it when unsure whether the person is signed in.' No alternatives are named, and none of the siblings appear to overlap with an identity check, so there is no meaningful exclusion to state.

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