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

With no annotations, the description carries the full burden and does disclose non-obvious traits: page size (~70 per page), a flat 13-credit cost whether cached or not, and refunds on failure. It does not state authentication prerequisites or confirm the read-only nature explicitly, but the cost/refund disclosure is well beyond what structured fields 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?

Front-loaded with the core action and pagination/cost facts packed into two sentences with little waste. The first sentence is dense with stacked clauses, but every clause earns its place.

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?

For a 5-param, zero-required, no-output-schema tool with no annotations, the description covers mode selection, page size, cursor semantics indirectly, cost/refund behavior, and the shape of returned items (counts and bio). Nothing critical for correct invocation 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 already 100%, so the baseline is 3, but the description adds value: it clarifies the mutual-exclusivity rule for `username`/`url` (neither is schema-required) and gives a concrete pagination quantity. It adds detail beyond the schema rather than restating it.

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 (fetch an account's followers / the accounts it follows) and covers both modes via `type=following`. It is distinguishable from neighbors like get_x_profile (profile details), get_x_retweeters (post-level) and get_tiktok_followers (different platform).

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?

Offers a use case ("Use this to see who an audience is") and a hard invocation constraint ("Give exactly one of `username` or `url`"), which is genuinely useful given both params are optional in the schema. However, it never names an alternative or a when-not condition, so usage is only implied.

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