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

Beyond the readOnly/idempotent annotations, it discloses the failure mode (404 when the List does not exist or is private) and the billing model (1 credit + 2 credits per list returned), which no structured field conveys. That is exactly the kind of behavioral context annotations cannot carry.

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?

Four short sentences, front-loaded with purpose then return fields, then alternatives, then error/cost. The only waste is the near-duplication between 'Billed per List returned' and 'Costs 1 credit + 2 credits per list returned.'

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 compensates by enumerating the returned fields, and it covers error behavior and pricing for a single-parameter read tool. Nothing an agent needs in order to call this correctly 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 coverage is 100% and the schema already explains that `id` is the digits after `/i/lists/` in a List URL, including the pattern. The description adds no further meaning about the parameter, 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?

Specific verb ('Get') plus specific resource ('a public X List') and an explicit statement of what metadata is returned (name, description, owner, member/follower counts). It also explicitly separates itself from get_x_list_members and get_x_list_posts, so an agent can place it among siblings without opening a schema.

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 routes the agent onward: members via `getXListMembers`, timeline via `getXListPosts`, making clear this tool only returns List metadata. It gives no explicit 'don't use for X' exclusion or prerequisite, but for a unique single-purpose lookup the guidance is clear.

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