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

Annotations already establish readOnly/openWorld/idempotent safety. The description adds valuable behavioral detail beyond that, such as '20 per page, cursor-paginated' and 'Returns full user objects under `members`.' This goes beyond what the annotations convey.

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 well-organized sentences: the first states the operation and pagination, the second gives the use case, and the third routes to alternatives. There is no filler, and the most decision-relevant information comes first.

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?

Given the output schema exists and annotations cover safety, this description is complete: it specifies pagination size, cursor mechanism, return field location, and sibling alternatives. Nothing an agent needs to invoke it 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 description coverage is 100%, so both `list_id` and `cursor` are already documented. The description adds only mild contextual meaning for `cursor` via 'cursor-paginated' but does not explain parameter formats or defaults beyond the schema. A 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?

The description opens with a specific verb and resource: 'List the accounts included in an X List.' It also distinguishes itself from nearby siblings like get_twitter_list_followers and get_twitter_list_tweets_timeline, so an agent can immediately tell what this tool uniquely does.

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 explicitly states when to use this tool: 'Use this to extract a ready-made, human-curated cohort — someone else has already done the filtering.' It also names two alternatives with their distinct purposes, giving clear routing guidance.

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