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

Annotations already convey readOnly, idempotent, non-destructive behavior recognising the safe read nature of the tool. The description adds useful context about the connection to household_id and the single-household case, which goes beyond the annotations, though it does not disclose response shape or pagination behavior.

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 sentences with no filler. The core statement is front-loaded empty and follow-up clarifies exactly when the tool is needed.

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-only list tool with an output schema, the description is nearly complete. It explains the meaning of the result set and the edge case that triggers its use. The only missing detail is what the output structure looks like, but the presence of an output schema reduces that need.

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 no parameters in the schema, so the schema provides no parameter semantics. The description compensates by explaining how the tool relates to household_id, even though household_id is not actually an input. This provides meaningful context for the tool's role, but there is little additional parameter detail to include.

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 exactly what the tool returns: households this user belongs to, including their ids. The additional sentence about when it is needed clearly differentiates it from the broader set of list_* siblings by tying it to the household_id disambiguation use case.

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 explicitly specifies when this tool should be used: 'Needed only when they belong to more than one'. It also tells the agent when to omit the household_id parameter and that omitting it resolves to their household. This is direct guidance for selection and invocation.

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