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

Annotations already cover the safety profile (readOnlyHint, openWorldHint, destructiveHint=false). The description adds genuinely non-obvious domain behavior: rewards exist in two states and in-review rewards are not owed because a human reviews each referral. That is real interpretive context the schema and annotations do not carry, though it says nothing about pagination or freshness.

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, purpose front-loaded, the critical warning placed second. The warning sentence is somewhat repetitive ('has not been approved and is not owed... may decide against it'), but the redundancy is defensible for an error mode that would otherwise cause incorrect sums.

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?

An output schema exists, so return structure need not be explained. The description covers what is fetched and the one interpretation rule that matters for this tool; the locale-driven language of results is fully handled by the schema. Nothing essential for a correct call is missing, though no routing guidance against siblings is given.

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?

Schema description coverage is 100% – from/to defaults and the locale enum usage are fully documented in the schema itself. The description only echoes 'over a date range' and adds no syntax, format, or constraint detail beyond what is already there. Baseline 3 applies when the schema does the heavy lifting.

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 a concrete resource and scope: 'Clicks, referrals and rewards for this affiliate over a date range, per service and in total.' An agent can tell this is the affiliate's own earnings summary rather than a provider-side operation. It does not explicitly distinguish itself from the close sibling my_referrals, which is why it falls short of a 5.

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 only guidance is about interpreting the output ('Approved and in-review rewards are two separate numbers... Never add them together'), not about when to select this tool versus my_referrals or my_account. There is no stated trigger condition for calling it and no exclusion stated.

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