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

Goes well past the annotations by disclosing the destructive side-effect in concrete terms: "One quiz per profile: a new one closes an unfinished one," consistent with destructiveHint=true. It also explains placement's side effects on card status (right promotes to known and leaves review, wrong stays in learning) and describes per-phrase result fields including score, reaction_ms and suggest_known.

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 lead sentence and the no-argument default are properly front-loaded, and length is defensible for 11 undocumented parameters. However, the body is a single dense prose block with heavy nested parentheticals, which makes the per-parameter rules hard to scan; a short structured list would carry the same content far more legibly.

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 no parameter descriptions in the schema, the description still covers modes, defaults, result shape ("known N, to learn M", per-phrase fields), and edge cases such as one-quiz-per-profile. An agent has everything needed to call it correctly on the first attempt.

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% across 11 parameters, so the description carries the full burden and does: it enumerates the values for type, source, mode and size (1-30) that the schema does not, and explains cross-parameter interactions such as card_ids nulling source and size, and repeat_of inheriting order and type. Tag is the thinnest entry (only "topic (with tag)" and its exclusion under placement), but every parameter is addressed with meaning beyond its name.

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 concrete verb and resource ("Start a quiz in the widget") and immediately explains the zero-argument default path. It implicitly distinguishes itself from quiz_after/quiz_save/quiz_end by covering saved sessions, repeats and placement variants, though it never names a sibling explicitly.

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?

Clear guidance on when to supply arguments versus rely on smart defaults, and which parameter selects which mode of use (terms vs card_ids, repeat_of vs saved, placement). There is no explicit exclusion such as "use quiz_after instead when...", which keeps it short of a 5.

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