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

Annotations already declare destructiveHint=true, idempotentHint=true, and openWorldHint=true, so the safety bar is partly met. The description adds genuine context beyond them: the mutation is limited to the name field, contacts are unaffected, and a dry_run preview mode exists. It does not explain why a rename is flagged destructive (e.g., the prior name is lost) or what permissions are needed.

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?

Three short clauses, front-loaded with the action and its scope, then the required inputs, then the preview option. Nothing is redundant and the most decision-relevant fact (contacts are not modified) appears early.

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 three-parameter rename tool with full schema coverage, annotations, and no output schema, the description covers the essential risk question an agent would have: whether contacts are affected. Only minor gaps remain, such as permission requirements and name-validation rules.

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 all three parameters are already documented in structured form. The description restates that list_id and the new name are required and glosses dry_run as a preview, but adds no format, constraint, or uniqueness detail beyond the schema.

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 names a specific verb and resource ('Update the name of an existing contact list') and bounds the effect ('Only the name changes, not its contacts'), which separates it from update_contact, update_segment, and update_campaign. It does not explicitly name a sibling to route away from, so it stops 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?

It gives useful scope context (rename only, contacts untouched) and points at dry_run for previewing, which implies when to reach for it. However, it never states when NOT to use it or which sibling handles contact membership changes, leaving tool selection to inference.

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