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

Annotations are all false and provide zero behavioral signal, so the description carries full burden — and it delivers. It discloses the 1-credit cost, that the deck is persisted to the user's account, a precise confirmation protocol for tentative requests, and the non-idempotent failure mode ('generating again spends another credit'). No contradiction with the annotations; idempotentHint: false aligns with the disclosed double-spend risk.

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 long but every sentence earns its place: cost, confirmation rule, prompt semantics, card-type limitation, return value, platform import guidance, credit-check avoidance, and failure recovery are all distinct payloads. The most critical facts (what it does, cost, confirm-first) are front-loaded. It is dense rather than bloated, though it could be tightened by merging the two confirm-first sentences.

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 and empty annotations, the description alone must cover behavior, cost, and return values — and it does, including 'Returns the cards, a link to the deck on NextLang... and the remaining credits.' The failure paths (low balance, timeout) are both handled with concrete recovery instructions. For a 6-parameter, side-effecting tool this is about as complete as a description gets.

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%, so the baseline is 3, but the description adds real meaning: it defines what 'prompt' can be ('a topic, a situation or a short text of up to 500 characters'), states that learningLanguage determines the card front, and constrains output to basic front/back cards — which shapes how prompt and language params behave. count and level are already richly documented in the schema, so the marginal addition here is meaningful but not exhaustive.

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 opens with a precise verb+resource: 'Generates a new flashcard deck with NextLang's own generator and saves it to the user's account.' The word 'new' explicitly differentiates it from expand_deck, and the generate/save semantics separate it from get_deck, save_deck, and add_vocabulary_items. The function is immediately distinguishable from all ten siblings.

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?

Exceptional. It explicitly says when NOT to use alternatives: 'Do not call get_credits first' and 'If this call fails or times out, call list_decks before trying again.' It also states the confirmation condition ('unless the user explicitly asked for a new deck, confirm first'), what not to promise (cloze decks are made on the website), and how to route Quizlet/Brainscape imports. This is the gold standard for sibling routing.

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