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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds real behavioral context beyond them: revisions recorded after the requested date are excluded (no hindsight leakage), and isExactDate=false signals the market was closed and the most recent earlier observation was substituted. That is exactly the kind of non-obvious behavior an agent cannot infer from 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?

Front-loaded with the core action, then the alternatives, then the caveats — a good ordering with no filler. Minor waste in restating the 100-symbol cap that the schema already enforces via maxItems.

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?

No output schema exists, so the description carries the burden of explaining return semantics — and it does, via the isExactDate explanation and the revision-exclusion rule. For a two-parameter read tool, nothing an agent needs to call it correctly 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 description coverage is 100%, so date format and symbol array bounds are already documented. The description's 'single symbol or up to 100' restates minItems/maxItems rather than adding syntax or format guidance, so the baseline of 3 applies; the isExactDate note describes a return value, not a parameter.

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 what mkts recorded about one or more symbols on a specific past date') plus the source ('immutable point-in-time archive'). It explicitly contrasts with the sibling get_assets_bulk, which serves current prices, so an agent can choose 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?

Gives concrete when-to-use cases (backtesting, reconstructing a past decision, checking whether a figure was revised) and an explicit when-not ('not for current prices, which get_assets_bulk serves'). The alternative is named along with the condition that selects it.

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