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

With no annotations, the description provides useful behavior beyond the schema: it notes '代码原样匹配' (exact symbol matching), the default symbol, and the mutual exclusivity of trade_date with start/end dates. It also lists the exact return fields. This is sufficient for a simple data retrieval tool, though it doesn't cover pagination, rate limits, or data availability.

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 tightly structured with separate Args and Returns sections, each line serving a purpose. It avoids fluff and front-loads the core purpose. Length is appropriate for the tool's complexity.

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 low-complexity data retrieval tool, the description covers all essential invocation details: what data is returned, the default symbol, and how to specify dates. The output schema exists, so listing fields is redundant but helpful. The only gap is the lack of sibling differentiation, but that's not required for correct usage.

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 the baseline is 3. The description repeats the parameter meanings and default values without adding new semantics. It does organize them cleanly, but no additional nuance beyond what the schema already provides.

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 '外汇日线（默认 USDCNH）' (Forex daily line, default USDCNH), clearly identifying the tool as providing forex daily OHLC data. This is specific and distinguishes it from sibling daily tools like 'daily' or 'etf_daily', which cover stocks and ETFs respectively.

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 implies usage for forex data via the asset class in the title and default symbol, but it does not explicitly state when to use fx_daily versus alternatives like daily or etf_daily. It also doesn't mention any exclusion criteria or scenarios where another tool would be preferred.

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