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

Annotations already cover the read-only/idempotent safety profile, and the description adds substantial non-obvious behavior: sampling and retention are bounded, a recorded print may differ from a live read, deltaMs is unsigned and measures sampling distance, and qualityRecorded is only populated for prints from 1 Oct 2026. The alias note further clarifies invocation behavior.

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-loads the core action and endpoint, then layers field-level caveats in short clauses. Dense and mostly waste-free, though the number of caveats (deltaMs sign, qualityRecorded cutoff, alias) makes it feel like a compact spec rather than a crisp summary.

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 two-parameter lookup whose safety profile is in annotations and whose return shape is in an output schema, the description supplies everything else an agent needs: nearest-sample semantics, bounded sampling/retention, unit ambiguity of the answer, and the alias. Nothing material 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?

Schema coverage is 50% (only symbol is documented), and the description compensates by stating the accepted formats for 'at' (ISO-8601 or epoch milliseconds), which the schema does not convey. It adds only partial interpretation guidance for that parameter, hence not a 5.

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 and resource ('Get the recorded signed index print nearest a requested time') with the backing endpoint, and distinguishes the resource from a live read ('a recorded print need not equal a separate live read'), which separates it from siblings like get_index_price and get_index_history.

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?

Gives concrete downstream guidance ('Check deltaMs', 'Preserve priceText, kid and the v2 block when present for verify_print') and discloses the legacy alias, so the agent knows how to consume the result and that the old name still works. It stops short of an explicit when-to-use-this-vs-the-live-read rule, so it is clear context rather than full routing.

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