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

Annotations already declare this as a safe, read-only, idempotent operation. The description adds useful domain behavior beyond those annotations: the conditional issuance of a referral code and the 5%/12-month commission terms.

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 three short sentences with no wasted text. The core purpose is front-loaded, followed by relevant commission context and a sibling pointer.

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 getter with rich annotations, the description covers purpose, issuance condition, business context, and the relevant sibling. It is mostly complete, though without an output schema it could clarify the exact return shape or behavior when no code has been issued.

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?

There are no parameters, so there is no parameter semantics to explain. The baseline for zero parameters is 4, and the description does not need to compensate for missing schema coverage.

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 states a specific resource, 'your own referral code', and its issuance condition. It explicitly distinguishes itself from the sibling get_referral_stats by noting that referred people are covered there.

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?

It clearly indicates when this tool applies ('if one has been issued') and routes referral-statistics queries to get_referral_stats. It does not explicitly mention apply_referral_code or other alternatives, but the usage context is clear.

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