List the address books

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

Beyond the annotations, the description adds a meaningful behavioral trait: 'Always asks the server rather than answering from a cache — being current is this tool’s whole job.' This informs the agent that freshness is guaranteed and that caching should not be assumed. No contradiction with annotations.

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 purposeful. The first sentence front-loads the core outcome (list of address books with IDs), and the second adds the non-obvious freshness behavior. No wasted words.

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 listing tool with an output schema present, the description fully covers what the tool does, how the results connect to other tools, and its key behavioral guarantee. Nothing essential 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 schema coverage is 100%, so there is no parameter detail to clarify. Per the 0-params baseline, the description is not required to add parameter semantics and does not need to compensate for any gap.

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 and resource: 'Every address book this server may use, with the id to pass to the other tools.' This clearly differentiates the tool from sibling list tools like list_contacts and list_groups by focusing on address books and their IDs.

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 clear context for when to use this tool: to obtain the list of available address books and the IDs needed by other tools. It does not explicitly name alternatives or exclusions, but the resource-specific purpose and mention of downstream use make the intended usage apparent.

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