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

Annotations already declare this is a non-readonly, non-idempotent, non-destructive write, so the safety profile is covered. The description adds one genuinely useful behavioral detail: omitting 'chunk' falls back to the right side of the correction or the whole rephrasing as a formulation. It says nothing about failure modes, duplication, or what is mutated, so it clears the lowered bar but does not enrich it much.

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 single dense sentence front-loads the purpose but then crams three parameter definitions plus a conditional fallback into semicolon-separated fragments, which hurts readability. Nothing is outright wasted, but the structure is tangled rather than crisp.

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 write tool with annotations covering the safety profile and no output schema, the description does not need to explain return values. It covers most parameters but omits the required turn_id and any notion of error or duplicate handling, so it is adequate rather than complete.

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 0%, so the description must carry parameter meaning. It usefully defines 'part' (correction or upgrade), 'index' (number in the review), and 'chunk' (expression number, with a documented default behavior). However, 'turn_id' — a required parameter — is never explained, leaving one of three required inputs undocumented in both schema and description.

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 opening clause 'Add to the vocabulary from a line review' does name a verb (add) and a resource (vocabulary entry), but 'line review', 'chunk', and 'formulation' are opaque jargon and the description never distinguishes this from the sibling vocab_add or add_cards. The purpose is only partially recoverable without domain knowledge of the app's review workflow.

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 guidance on when to use this tool versus vocab_add, add_cards, or practice_phrase, all of which appear to touch vocabulary. The description explains internal field mechanics rather than selecting conditions, leaving the agent to guess the triggering context.

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