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

Beyond readOnlyHint/idempotentHint annotations, the description discloses that this is a retrospective replay rather than a live append-only record, that both winning and losing replay signals are included, that the open book is bounded and marked at last close, and that the output is signal data rather than investment advice. This adds meaningful behavioral context beyond the annotations.

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?

Four sentences, front-loaded with the use case and return contents. Each sentence earns its place: the trigger, the output summary, the inclusion of both outcome types, the replay-vs-live distinction, and the disclaimer. No filler or redundancy.

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 an output schema present, return values need no further explanation. The description covers the time window, the engine being replayed, the closed-signal metrics, the open book page, the replay/live distinction, and the not-advice caveat. Nothing essential is missing for correct invocation.

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 the schema already explains open_limit and open_offset fully. The description's mention of the 'bounded page of the open book' gives some contextual framing for the paging parameters, but it does not add significant semantic value beyond 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 opens with a specific use case ('whether Hesper Atlas's headline track record is supported') and clearly states the resource: headline performance of today's trend engine replayed over up to five years of historical EOD data. It also distinguishes itself from an 'append-only live record,' which separates it from forward-looking 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?

The 'Use when...' phrasing gives explicit trigger scenarios: checking whether the headline track record is supported, or wanting winning, losing, and still-open periods. It also states what the tool is not ('not an append-only live record'), but it does not name the specific sibling tool to use instead, so the guidance is clear but not fully explicit about alternatives.

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