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

Annotations already establish readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description usefully adds behavior the annotations do not: the public-account restriction, that a total follower count is returned, that pagination is cursor-based and only sometimes available, and an explicit cost of 3 credits.

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?

Short and front-loaded: the operation and scope come first, followed by pagination and cost. The first two sentences overlap slightly ("followers" and "public follower list of a public account"), a minor redundancy rather than bloat.

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 does the necessary work of describing what comes back (follower list plus total count) and how paging works. Cost is disclosed. It omits any auth/access prerequisites beyond "public account," but is complete enough for an agent to call it 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 the schema already documents cursor, user_id and username in detail (including the either/or relationship and @-handling). The description adds only a vague note that paging uses a cursor "where available," so this lands at the baseline for a fully documented schema.

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 gives a specific verb and resource ("Get an account's followers") and adds a meaningful scope constraint: it returns the public follower list of a public account, with the total follower count. That is far clearer than a name restatement, but it never explicitly contrasts itself with the mirror-image sibling instagram_following, which is the main confusable alternative.

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?

Usage is only implied: the phrase "of a public account" signals this only works for public accounts, and "where available" hints pagination may not always exist. There is no explicit when-to-use guidance and no mention of when to choose instagram_following or instagram_profile instead.

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