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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds two genuinely useful behavioral facts the annotations do not: a 50-per-page page size and the existence of a next_page cursor. It says nothing about ordering defaults or error/auth behavior, so a 3 is right.

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?

Two sentences, no filler: the resource and page size come first, the scope semantics second, the endpoint last as a precise anchor. The long enum gloss is dense but every clause disambiguates a real choice the agent must make.

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?

There is no output schema, and the description compensates by stating the page size and implying the cursor-based continuation documented on the page parameter. It stops short of describing the shape of a referral record, but for a read-only listing tool with a fully documented schema this is nearly sufficient.

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 goes further by explaining what each scope value actually returns (confirmed-only vs all statuses per referral level) where the schema only says 'Which referrals (default all)'. Page, sort_by, uuid and subscriber_id are left entirely to the schema, which documents them well.

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 opens with a concrete verb-implied resource statement ('The people a subscriber referred') and pins the exact endpoint, so an agent can tell this apart from referralhero_list_subscribers. It does not explicitly name the sibling it differs from, which keeps it short of a 5.

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 context is only implied through the scope enumeration (e.g. level_2_all = 'every status at that level'), which tells the agent which scopes exist but not when to pick this tool over get_subscriber or the reward-listing tools. No explicit when/when-not guidance is present.

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