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

Annotations already declare readOnlyHint=true, so the safety profile is clear. The description adds useful return-shape context: it lists returned fields, explains that contacts are excluded, notes that an empty result is returned when there are none, and names the REST endpoint, which is meaningful beyond the annotation.

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 definition is front-loaded and compact: the core purpose and return shape come first, followed by a useful empty-result note and the REST endpoint. It is appropriately sized, though the endpoint line is slightly less essential for tool selection than the rest.

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?

With no output schema, the description adequately explains the returned fields and the empty-result behavior. Pagination is covered by the fully documented skip and limit parameters, and the read-only nature is covered by annotations, so nothing needed for correct invocation 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?

Schema description coverage is 100%, so skip and limit are already fully documented in the input schema. The description adds no parameter-specific meaning or format details beyond what the schema provides, making the baseline 3 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 uses the specific verb 'List' with the resource 'contact lists' and enumerates the returned fields (id, name, status, size, created/updated times). The phrase 'without their contacts' clearly distinguishes it from get_contact_list, which would retrieve a single list with its contacts.

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 implies usage by contrasting this summary list with fuller contact retrieval, but it does not explicitly state when to use this tool versus get_contact_list, create_contact_list, or update_contact_list. No exclusions or conditions are named, so the guidance is implied rather than explicit.

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