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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so safety is covered. The description adds real behavioral context beyond that: it is a pre-flight check that 'measures nothing', and it discloses the shape of its findings (usable vs. unusable history, closest listing). It does not mention limits such as the 150-ticker cap or rate/latency behavior, but the added scope clarification is meaningful.

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 what the tool does and its three outputs, then the when-to-use rule and alternative, then the base nuance, closing with the scope boundary ('It measures nothing'). Every clause carries information and none is wasted.

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?

An output schema exists, so return values need not be spelled out; the description still summarizes them helpfully. Purpose, routing to the sibling tool, and the one non-obvious parameter behavior are all covered for a two-parameter read-only validator.

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 100%, so the baseline is 3. The description goes further than the schema's 'Currency every figure is expressed in' by explaining that base prioritizes the listing in that currency when a symbol trades in several markets — a tie-breaking semantic the schema does not state.

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 (checks a list of tickers) and enumerates the three concrete outcomes it returns: which have usable price history, which do not, and the closest listing for ambiguous symbols. It is clearly distinguishable from siblings like search_symbols and measure_portfolio.

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 an explicit when-to-use condition ('when the tickers are already written down') and names the alternative plus its triggering condition ('when only a name is known, search_symbols'). Nothing is left to inference.

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