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

The description goes well beyond the annotations by detailing the error behavior ('never raises a protocol error'), the exact interval schedule, and the return format. It confirms the readOnlyHint and idempotentHint annotations with plain language, and adds that it's safe to retry after correction. No contradictions with annotations.

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 well-structured with a short opening, a code example, usage rules, and error handling. Every sentence adds value, but there is minor redundancy (e.g., the interval list and example overlap slightly). It could be trimmed slightly without losing meaning.

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?

Given the tool's moderate complexity (2 params, simple output), the description fully covers purpose, usage, parameters, errors, and idempotency. The output schema exists, so the description doesn't need to detail return values. The combination of description, annotations, and schema is complete for effective use.

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 schema already covers both parameters with descriptions and defaults, so the baseline is 3. The description adds value by showing a concrete example input and output (e.g., 'sessions': 4 returns 4 review dates), and hints at clamping behavior. However, it does not fully explain the 'sessions' default or clamping range beyond what the schema states.

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 clearly states the tool builds a spaced-repetition review schedule with expanding intervals, which is a specific verb+resource combination. It distinguishes itself from siblings by providing explicit interval details and a usage example, and none of the sibling tools appear to overlap with this functionality.

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 description explicitly says when to use it ('material must be reviewed on expanding intervals') and when not to ('not for timing a single session'), and names the alternative tool ('lesson_timer'). It also provides guidance on error handling and retry behavior, making usage boundaries exceptionally clear.

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