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

Annotations already declare readOnlyHint, non-destructive and non-open-world, so the safety profile is covered. The description adds genuinely new behavioral context: the mutual credit reward when a friend completes a first transcription, plus that a limit appears in the result. It does not describe auth requirements, but for a read-only self-scoped fetch the added reward semantics are the salient non-obvious trait.

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 resource and then the constraint, with no filler. The first sentence is slightly convoluted by the colon construction, but every clause carries information about the return value or the credit rule.

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 must convey the return content, and it does: the link itself plus the accrued credit status and a limit. For a zero-parameter read-only tool this is essentially complete, with only minor gaps around the exact shape of the result.

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 there is no parameter semantics to explain and the baseline of 4 applies. The description correctly implies the operation is scoped implicitly to the signed-in user with no inputs required.

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?

States a specific resource and scope: 'the signed-in user's own invitation link', plus what it returns (the credit-earning status of that link). This is clearly distinguishable from every sibling, none of which deal with invitations or sharing.

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?

Gives an explicit trigger ('use only when the user asks to invite or share') and an explicit exclusion ('never push it unasked'). No alternative tool exists for this purpose, so the routing guidance is complete.

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