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

Annotations already establish readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so safety is covered. The description adds genuinely useful behavior beyond that: the per-account return shape ('profile details'), the pagination rate (~50 per page), and the cost model ($0.006 per page), which matters for a paginated paid call.

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 sentences, zero filler, with the core purpose front-loaded and the cost/pagination facts appended in the order an agent needs them.

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 stating what each returned item contains and how many per page, plus the billing model. It stops short of noting rate limits, auth requirements, or truncation behavior for very large following lists, but it is sufficient to call the tool correctly.

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 (username, pages with 1-175 range) are already documented in the schema. The description's '~50 per page' restates the schema's page-size note rather than adding new semantics, so 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 and resource ('Get the accounts a Twitter/X user follows, by username'), which is unambiguous and clearly distinct from a search tool. It does not, however, name the closely related siblings (twitter_user_followers, twitter_verified_followers) to rule out confusion in the 'following vs followers' pair.

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?

There is no explicit guidance on when to use this versus twitter_user_followers, twitter_verified_followers, or twitter_user_profile, all of which sit adjacent in the tool list. Usage is only implied by the tool's name.

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