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

Annotations only cover readOnlyHint/openWorldHint, so the description carries real load and delivers: pagination contract (has_next_page + next_cursor, feed next_cursor back as cursor), a tiered credit cost model, and a 15-per-call minimum with a bulk waiver. It omits error/rate-limit behavior and auth requirements, but the cost and pagination disclosure is well beyond what the annotations provide.

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, front-loaded blocks — purpose first, then pagination, then cost — with no filler sentences. Every line earns its place and the routing rationale leads.

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 adequately describes the return shape (ids only, plus paging fields) and the cost model. The one gap is that it never clarifies how the target account is identified, notable given 0 required parameters and both userId/userName being optional.

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 0% with 4 parameters, so the description must compensate. It explains cursor semantics ('pass next_cursor as cursor for more') which is genuinely useful beyond the bare default of -1, but it says nothing about how userId vs userName select the target or what count/default 5000 means, leaving half the parameters undocumented in both places.

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+resource ('Return follower ids only') and immediately distinguishes itself from the profile-returning siblings by emphasizing IDs-only output and pagination. An agent can tell it apart from user_followers / list_followers / user_verified_followers 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?

Gives clear context: 'The cheapest way to snapshot a big follower graph before hydrating the profiles you care about' tells the agent when this tool is the right first step versus fetching full profiles. It does not explicitly name the sibling to use for hydration, so it stops short of full routing guidance.

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