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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive, so safety needs no restating. The description adds real behavioral value by enumerating the returned content categories and capping topics at 6 (up to 6 deck topics plus no_topic), which the annotations cannot convey.

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 main purpose is front-loaded and there is no filler, but the phrasing is garbled ('over days days', 'most words in work') and reads as a compressed field dump, forcing the agent to reparse rather than understand immediately.

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 describe returns, and it does list the main sections. However, the cryptic topic field names (added, in_work, learned) and the broken day-window phrasing leave an agent uncertain about the exact response shape for a stats tool with several output sections.

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?

One parameter (days, default 14) with 0% schema description coverage, so the description carries the burden. It references the day window ('over days days') but adds no units, bounds, or clarification on whether the window includes today, leaving the parameter only partially explained.

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 states a specific verb+resource: a learning-progress summary over a day window, listing cards, reviews, activity by source, recent pronunciation attempts, and topic breakdowns. An agent can tell this is a statistics/digest tool, though it never explicitly contrasts itself with sibling stats tools such as word_stats, lesson_progress, or today.

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 or when-not-to-use guidance. The 'over days days' phrasing implies a rolling window, but nothing indicates which sibling to pick when an agent needs per-word stats (word_stats) or lesson-specific progress (lesson_progress).

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