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

Annotations already declare destructiveHint, idempotentHint and a closed world, so the description's added value is in disclosing immutability ('a saved review cannot be changed') and that the updated schedule is returned. The retry/idempotency story is left to the schema, which is reasonable.

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?

Three tight sentences with no wasted words. The prerequisite is front-loaded, though placing a precondition ahead of the purpose statement is slightly less scannable than leading with what the tool does.

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 a rich schema and an output schema, the description only needed to cover the guide prerequisite, immutability, and the scheduling effect — all of which it does. Nothing an agent needs to call it correctly is missing.

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 coverage is 100%, so every parameter including the rating enum and reviewId retry semantics is fully documented in the schema. The description adds no parameter-level detail beyond what is already structured, making 3 the correct baseline.

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 verb and resource ('Records the rating', 'advances the card's authoritative FSRS schedule') and names the effect and return value. It is clearly distinguishable from siblings like next_review_card or reveal_answer.

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 prerequisite ('Before the first grading in a conversation, read get_guide(review_flow) and follow it') and an exclusion ('Past reviews cannot be imported'). It does not explicitly contrast against sibling tools or state when grading should not be submitted, so it falls short of a 5.

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