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

With annotations covering the mutation and idempotency profile, the description goes well beyond that: it names the downstream effects (moves the word's box, updates the day's numbers and streak), says the result carries the next review date, and explains the practice path where scheduleChanged is false. The client_id deduplication note reinforces the idempotentHint in plain language.

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, front-loaded with the core action, then the side effects, then the edge case and idempotency. Every sentence carries information an agent would otherwise have to guess.

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?

For a three-parameter mutation with full schema coverage, an output schema, and annotations, the description supplies exactly what structured fields cannot: what changes in the app state, the practice/not-due special case, and deduplication semantics. Nothing needed 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 description coverage is 100%, so all three parameters are already documented in structured fields. The description mentions client_id and its double-submit behavior, but this largely restates the schema's own description. Baseline 3 is appropriate; no meaningful syntax or format detail is added.

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 whether the user answered a practice question about a word correctly.' It is clearly distinguished from every sibling (which manage words, meanings, notebooks, or listings) and leaves no ambiguity about what calling it does.

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 establishes the usage context implicitly through the practice-not-due-word case, and no sibling tool competes for this action. It stops short of explicitly saying when to call it rather than, say, get_due_words, but the context is clear enough that an agent won't misroute.

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