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

Beyond the readOnly/idempotent annotations, the description discloses the snapshot nature, the reason for it (FRED blocks workers), the payment requirement, and the behavior on unpaid calls. This is thorough transparency about how the tool behaves.

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 compact and well-structured: it leads with the data provided, then explains the snapshot nature, then the cost/payment, and finally the equivalent HTTP route. Each sentence adds value without redundancy.

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?

The description covers the data, snapshot mechanism, cost, and check instructions, which is sufficient for usage. It does not explicitly define the response format, but mentions the snapshot fields, so it's mostly complete. Slightly more detail on the response structure would push it to 5.

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 already documents the 'as_of' parameter with a clear description. The tool description adds nothing further about this parameter, so it stays at the baseline. No additional clarity is provided beyond the schema.

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 resource (US Treasury yields) and lists the specific data points: 2, 10, 30 year yields, 10s2s spread, and mortgage rate. It also clarifies it's a stored snapshot, distinguishing it from live data tools. This is unambiguous and actionable.

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 provides explicit usage guidance: check snapshot.captured_at and snapshot.age_hours before trading/quotes, explains that it's refreshed out of band due to FRED blocking, and details the payment mechanism (cost, unpaid challenge, no settlement on no data). This helps the agent decide when and how to use it.

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