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

The annotations already cover the safety profile (readOnly, non-destructive, not open-world), so the description is free to add domain rules, and it does: free bags are only granted when a Never Run Dry subscription is active, which is a real business rule an agent can't see in the schema. It also implicitly discloses that the tool is scoped to the calling user. It stops short of saying what the redemption objects look like, but that is minor given there is no output schema.

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?

It is a single sentence that front-loads the returned fields and puts the conditional eligibility rule in parentheses, so there is no wasted prose. It is a list of fields without framing, but it is tight for the scope.

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 carries the job of enumerating return values, and it lists four of them plus the eligibility precondition. It is complete enough for an agent to decide when to call it, though it doesn't say what an empty or ineligible state looks like.

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 takes no parameters, so it earns the baseline of 4 by default. The description correctly implies a caller-scoped read with no inputs to pass.

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 names the specific resource it returns: the caller's referral code, redemptions, Pack Points, and free-bag eligibility. It is clearly a read of referral data and does not overlap any sibling such as get_my_pack or get_player_status, though it never uses an explicit verb like 'get'/'return'.

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?

Whether to use this tool is implied by its name and fields: use it when you need the caller's referral status. There is no explicit statement of when to prefer it, and no exclusions or alternatives are named; for a zero-parameter tool this is adequate, but usage is not spelled out.

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