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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile needs no repetition. The description adds program semantics (one free month per paying signup, 30-day trial for the friend) that help the agent explain the result, but it does not disclose whether a link always exists or what happens if the user has no referral program.

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, front-loaded with the returned artifact. The second sentence is reward-program context rather than invocation guidance, so it is slightly padded, but it is short and plausibly useful for answering user questions about the link.

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 burden of describing the return value, and it does identify two artifacts (link and code). It does not state the format (e.g., a URL string plus an alphanumeric code, or a single combined payload), which is a minor residual gap for a read-only single-purpose tool.

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 zero parameters, so the baseline is 4 and there is no parameter behavior the description could add or omit. The schema is trivially complete.

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 returned: a personal referral link and code. It is a noun phrase rather than a verb-fronted statement, but for a zero-parameter getter the intent is unmistakable, and no sibling tool (account, history, vehicle status, controls) overlaps with it.

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 is only implied: the agent is expected to call it when the user asks about referring a friend or wants their link. There is no explicit when-to-use or when-not-to-use statement, though with 21 siblings and no competing referral tool, there is little ambiguity to resolve.

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