get_etf_performance

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

No annotations are provided, so the description carries the full burden. It states it retrieves historical performance but does not disclose whether it is a read-only operation or any potential side effects (unlikely). It also does not mention if the tool returns absolute or percentage returns, or if it includes dividends. Since it's clearly a read-only data fetch, the lack of disclosure is minor but could be improved.

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 a single, clear sentence with no fluff. It efficiently communicates the core purpose and lists the accepted period values. It is appropriately brief and front-loaded with the main action.

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 simple read tool with only two parameters and no output schema, the description is adequate. It covers what the tool does and the inputs. However, it lacks information on what the output looks like (e.g., a chart, a list of numbers) and what the default period is (though the schema states defaults), which could be clarified. Given the simplicity, it meets the minimum viable standard.

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 schema provides 100% coverage for both parameters, describing each adequately. The description does not add extra meaning beyond the schema, such as the exact format of the symbol or the default behavior of the period. The schema already notes that period defaults to 1y, so the description adds little value.

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 clearly states the tool's purpose: retrieving historical price performance for an ETF over specified periods. The verb 'Get' and resource 'historical price performance' are specific. However, it does not explicitly distinguish it from siblings like get_etf_quote or get_etf_summary, though the focus on performance periods is fairly unique.

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?

It mentions the 'given period' and lists valid periods, but there is no explicit guidance on when to use this versus alternatives. The description implies it is for performance data, but does not mention when not to use it or suggest siblings.

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