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

No annotations exist, so the description carries the full burden, and it does disclose real operational traits: a fixed 3-credit cost regardless of cache, and a refund on failure. It omits auth requirements, rate limits, and error mode distinctions, so it is strong but not complete.

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?

Four compact clauses ordered as payload, usage, input constraint, then cost — front-loaded with what the caller gets. The dense em-dash field list is slightly run-on 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?

With no output schema, the description usefully enumerates the return fields and their X API v2 naming, and it covers cost/refund and the input constraint. Missing auth/prerequisite detail keeps it from 5, but nothing needed to call it correctly is absent.

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 100%, so the baseline is 3, but the description adds the mutual-exclusivity rule ("exactly one of username or url") that the schema does not encode — required is empty and there is no oneOf. That is genuine meaning beyond the structured fields.

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 ("Fetch an X account") and enumerates the returned fields (username, name, description, location, link, verified, created_at, public_metrics). It is clearly an account-level lookup rather than a post/follower call, but it never names or contrasts with the many get_x_* siblings, so it stops short of the 5 bar.

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?

"Use this to size an account or enrich a handle" gives a clear selection context, and "Give exactly one of `username` or `url`" is an explicit input rule. There is no when-not guidance and no named alternative (e.g., search_x for discovery), so it is clear context without exclusions.

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