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

Goes meaningfully beyond the annotations by disclosing the quota cost ('Spends one of the user's Ask questions for the day'), the answer shape (~350 words, numbered sources, states when its record is thin), and the asynchronous fallback to get_ask_answer. The openWorldHint explains why answers may be thin, but nothing is said about what happens when the quota is exhausted.

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 selection condition and tightly packed with decision-relevant facts; nearly every clause earns its place. Some sentences are run-on (the parenthetical examples and the record/papers list), which slightly hurts scannability.

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, the description still covers the return shape (length, numbered citations, honesty about thin coverage), the async answer-retrieval path, the quota side effect, and the follow-up mechanism. An agent has everything needed to call it, wait, or retrieve the result.

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 both parameters are already fully documented, including language handling and the conversation_id pattern. The description's 'Pass conversation_id for a follow-up' only restates the schema rather than adding new semantics, so the baseline 3 applies.

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 ('written, cited answer') and resource ('research question on the biology of aging...'), and immediately contrasts with the sibling that returns papers: 'rather than a list of papers... For the papers themselves, use search_papers.' An agent can route between ask_arn and search_papers without opening either 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?

Explicit positive triggers with worked examples ('does rapamycin extend lifespan in people, who works on epigenetic clocks'), an explicit exclusion ('Not for personal medical advice, doses or symptoms'), a named alternative for the list case, and follow-up routing via conversation_id plus get_ask_answer when the answer is not ready.

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