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

Annotations already declare destructiveHint=true, and the description reinforces this with 'this MODIFIES live data', which is consistent and useful emphasis. It adds the endpoint and return shape, but omits behavior an agent would want for a mutation: duplicate-name handling, required auth/scopes, and error 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?

One short sentence with the mutation warning front-loaded, followed by the endpoint and return value. Every clause carries information, with only minor redundancy against the title 'Create list'.

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 one-parameter tool whose annotations cover the safety profile, the description covers action, mutating nature, endpoint, and return value. No output schema exists, and return behavior is briefly noted, so little is missing for correct invocation.

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 the single parameter is already documented as 'Human-readable name for the new list.' The description's 'Provide a `name`' adds no syntax, constraint, or format detail beyond the schema, so the 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 specific verb+resource ('CREATES a new list') and the backing API call (POST /lists), so the action is unambiguous. It doesn't explicitly distinguish itself from siblings like emailoctopus_create_contact or emailoctopus_update_list, though the resource name makes the distinction largely self-evident.

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?

Says only 'Provide a `name`' with no when-to-use context, no prerequisites, and no comparison to alternatives such as update_list. An agent gets no guidance on when this is the right tool versus a sibling.

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