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

Annotations already mark the tool as readOnly, idempotent, and non-destructive. The description adds substantial behavior beyond that: it requires an active Hesper Atlas subscription, returns only the latest completed end-of-day state, and explains that `action` and `suggested_position` are authoritative once a trigger is crossed. It also includes the 'signal data, not investment advice' caveat.

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 dense but structured: a front-loaded usage directive, a colon-introduced list of return fields, and concise caveats. Every sentence adds information; the field list is arguably long but necessary given the tool's specificity.

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 single-parameter, read-only tool with an output schema and annotations, this description is complete. It covers when to use it, subscription requirements, what data is returned, field authority semantics, and a legal disclaimer. Nothing essential is missing.

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?

The input schema fully documents the single `symbol` parameter with a description, example, and case-insensitivity note (100% schema coverage). The tool description adds no new parameter-level detail beyond referring to 'one ticker', which matches the baseline expectation for a fully covered 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 ('Use when an authorized user asks for the latest Hesper Atlas action on one ticker') and names the exact resource ('latest completed end-of-day state'). It clearly distinguishes itself from replay data and subsequent sibling tools by scoping to a single ticker and the current signal.

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 description gives a clear when-to-use condition (authorized user, latest action, one ticker) and explicitly instructs not to substitute replay data if access is missing. It mentions the subscription prerequisite, but does not explicitly name sibling alternatives such as list_signals or get_symbol_record, so it stops just short of full alternative routing.

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