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

With no annotations, the description carries full responsibility for disclosing behavior. It explains the output structure (names and slot names), the accessibility rules (values readable only by writer unless public, then address given), and confirms slot names are public. This gives an agent a solid understanding of what the tool returns and the visibility semantics. It does not explicitly state that it is a read-only operation, but that is strongly implied by the listing nature. Minor gap: it doesn't mention potential pagination or ordering, but for a no-arg tool this is acceptable.

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 with zero filler. It opens with the core purpose, immediately clarifies what it is not, and then provides the essential visibility rules. Every sentence adds critical information, and the structure front-loads the primary function. It is concise yet comprehensive.

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 no-argument tool with no output schema, the description fully explains what the agent should expect: a list of names and slot names, with clarity on the public/private distinction. It covers the key edge case (slot values visibility) and confirms that slot names are always public. Nothing an agent needs to correctly interpret the result is missing.

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, and the input schema is empty. Per calibration, baseline for 0 params is 4. The description adds no parameter-specific information because there are none to describe. It does clarify what the output represents, which is indirectly relevant but not parameter semantics. The baseline score is appropriate.

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 verb ('holds a locker') and a clear resource ('every name that holds a locker here'), and specifies exactly what it returns: names and slot names. It immediately distinguishes itself from tools that retrieve slot values (locker_get, locker_put) by explicitly saying 'Not what is in them.' This provides clear differentiation from sibling tools.

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?

While the description does not explicitly name sibling tools, it clearly implies when to use it: when you need to know which lockers exist and what their slots are called, not when you need to read or write slot values. The phrase 'Not what is in them' serves as an implicit exclusion, guiding an agent toward locker_get or locker_put for value access. This is clear enough for selection, though it could be more explicit about alternatives.

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