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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is fully covered. The description adds the one-model scoping constraint and the filter-key use case, but says nothing about pagination, ordering, or result envelope, and there is no output schema to fill that gap.

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?

A single front-loaded sentence with the scope and model stated first, followed by the action-oriented rationale. No filler and nothing buried.

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 two-parameter, read-only list tool with an output schema absent but a simple return shape, the description covers scope, the required selector, and the practical reason to call it. Only the return/pagination behavior is left unaddressed, which is a minor gap.

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 both parameters are already documented by the schema, including the attribute_model enum values. The description only restates the enum and mentions attribute_key as an obtainable field, adding no syntax or format detail beyond the schema; baseline 3 is 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?

States a specific verb ('List') and resource ('custom attributes'), and adds the account scope plus the model selector (conversation_attribute or contact_attribute). This distinguishes it from the sibling get_details_of_a_single_custom_attribute, which retrieves one record rather than enumerating.

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?

Gives concrete usage context: 'Call before creating or changing one, and to learn the attribute_key an automation rule or bot can filter on.' That covers when-to-use well, but it never names the adjacent sibling tools (get_details_of_a_single_custom_attribute, create/update/delete_custom_attribute) as explicit alternatives or exclusions.

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