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

Beyond the read-only annotations, the description discloses real behavioral nuance: that dueToday is every due word while today is the subset the app's practice engine schedules under the notebook's reviewsPerDay, with 0 meaning no limit. That distinction is exactly the kind of non-obvious semantics annotations cannot carry. It stops short of saying when the counts are computed or whether they include retired words.

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?

Front-loaded with the field inventory, then a targeted disambiguation of dueToday versus today. Dense but every clause earns its place; the final sentence is long yet cannot be cut without losing the reviewsPerDay 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?

One optional parameter and an output schema means the description needn't explain return shapes, and it still adds the one interpretive rule an agent would otherwise get wrong. Only the lack of guidance against sibling tools keeps it from full marks.

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% and the single parameter is documented there, so the schema does the heavy lifting. The description adds no new detail about notebook_id itself, and its clarifying work is about output fields rather than the input.

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?

Names the resource (notebook) and enumerates exactly which counters come back – words, due today, new, mastered, struggling, starred, hard to spell – plus streak, which no sibling returns. A verb is implicit ('per notebook: how many'), so it is not a textbook verb+resource statement, but an agent can tell this apart from list_words or get_due_words immediately.

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?

There is no explicit when-to-use, when-not, or named alternative; the only scoping hint ('omit for every notebook') lives in the schema. Nothing tells the agent whether this is the preferred way to see due counts versus get_due_words, which is the key routing decision here.

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