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

Annotations already declare readOnlyHint=true, so the safe-read profile is covered; the description adds the backing endpoint (GET /contact_books), which corroborates a non-mutating read. It does not disclose return format or pagination behavior beyond what the schema implies, so with annotations the bar is met at a 3.

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 compact clauses, front-loaded with the verb and resource, with the endpoint reference appended. Every token earns its place; 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 simple zero-required-param read-only list tool with full schema coverage and no output schema, the description covers what is needed to invoke it correctly. Only minor gaps remain around ordering/return shape, which the schema partially implies.

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?

Schema description coverage is 100%, and both parameters (limit, offset) are fully documented in the schema including defaults and max. The description adds nothing on parameters, so baseline 3 applies.

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?

States a clear verb+resource ('List contact books') and parenthetically disambiguates it as address books, which helps separate it from sibling list_contacts and list_contact_groups. It does not explicitly contrast those siblings, so it stays 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?

No guidance on when to use this tool versus the many sibling list tools, and no stated prerequisites or exclusions. The only hint is the resource name itself.

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