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

Annotations only state it is a non-readOnly, idempotent, non-destructive write; the description adds the meaningful outcome (a stamp in the passport) and the answer-matching rules (case, accents, articles, plurals and units ignored). It does not disclose the failure path for an incorrect answer or any rate/attempt limit, which is the main remaining gap for a mutating tool.

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?

Front-loaded with the core action and the pointer to where n comes from, and the format rules are dense but each is operative. It is slightly list-like in the answer-format clause but nothing is padding.

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 four-parameter write tool with no output schema and thin schema descriptions, the description covers the challenging parts (challenge indexing, acceptable answer shape, reward). What an incorrect answer produces, and which fields the response contains, remain unstated.

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?

With only 25% schema coverage, the description carries the burden and largely does: it defines 'n' (1-based, sourced from capa.retos) and specifies the answer's form and normalization rules. piece_id and visitor_name get no additional meaning here, though visitor_name is already documented in the schema.

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 names a specific verb (answer) and resource (one of a piece's challenges), and pins down the indexing convention ('n starts at 1; see capa.retos in get_piece'). An agent can distinguish this from siblings like get_piece or submit_hunt without inspecting any schema.

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?

It tells the agent where the answer comes from (look closely at the piece) and how to locate the challenge list via get_piece, which implies the prerequisite call. It also adds an explicit constraint ('Do not list several options'). It does not say what to do after a wrong answer or whether retries are allowed, so it stops short of full when/when-not guidance.

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