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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds context about what the tool returns (referral link, bonus summary, referred users) but does not disclose details like whether the bonus is capped, how qualification works, or pagination. It doesn't contradict annotations, but it doesn't add much beyond the annotations.

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?

The description is a single sentence that front-loads the core purpose ('Refer-a-friend status') and then elaborates with three specific components. It is concise and structured, though the parenthetical about capped cash bonus could be seen as slightly dense. No wasted words.

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 zero-parameter read-only tool with no output schema, the description covers the main return values (referral link, bonus summary, referred users). However, it doesn't explain the bonus qualification process or the cap details, which could be relevant for an agent deciding whether to call this tool. The annotations cover safety, so the description is adequate but not fully complete.

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?

The tool has zero parameters, so the schema provides no parameter documentation. The description compensates by explaining what the tool returns, which is the relevant semantic content. With no parameters to document, a baseline of 4 is appropriate because the description clarifies the tool's scope and output.

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 clearly states the tool's purpose: retrieving refer-a-friend status, including the referral link, bonus summary, and referred users. It uses a specific verb ('get') and resource ('referrals'), and the title 'Referral status' reinforces this. It is distinguishable from siblings like split_get_earnings and split_list_campaign_bonuses, though it doesn't explicitly name them.

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?

The description implies usage context (checking referral status) but does not explicitly state when to use this tool versus alternatives like split_get_earnings or split_list_campaign_bonuses. It provides no exclusions or conditions. The context is clear enough for an agent to infer, but it lacks explicit routing guidance.

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