米イールドスプレッド（10y-5y）

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

With no annotations provided, the description carries the full burden. It discloses that the tool returns the spread and day-over-day change in basis points, and characterizes the output as 'reference information'. However, it does not discuss data sourcing, update frequency, or behavior under extreme conditions (e.g., no data).

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 two sentences with no wasted words. It front-loads the core function (return spread), provides technical details (symbols, bp), and concludes with practical context (reference for decisions). Perfectly sized.

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?

Given no output schema, the description explains what is returned (spread value and bp change) and its significance. It could be slightly more explicit about the return format (e.g., decimal or basis points), but the inclusion of 'bp' strongly implies basis points. The simplicity of the tool (no parameters) makes this adequate.

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 input schema has no parameters (100% coverage trivially), so the baseline is 4. The description adds significant value by explaining what the return value represents (spread, positive/negative yield curve, bp change), which is essential for correct interpretation.

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 returns the yield spread between US 10-year and 5-year bond yields, specifying the exact instruments (^TNX, ^FVX) and explaining the meaning of positive/negative spread. This differentiates it from siblings like get_quote (individual yields) and get_market_snapshot (broader market data).

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 use for investment decisions related to yield curve analysis but does not explicitly state when to use this tool over alternatives or provide exclusions. The context is clear enough given sibling tools that handle different aspects, but no direct comparison is made.

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