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

With no annotations, the description carries the full burden and largely meets it: it discloses the non-obvious weekend/holiday fallback to the prior business day (returned with a note), the unit and tenor coverage, and the upstream source. It does not explicitly state that the call is a side-effect-free read or address rate limits/caching, which keeps it below a 5.

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?

Three short sentences, front-loaded with what the tool returns and its scope before the edge-case behavior. The trailing 'not financial advice' is a disclaimer rather than invocation-relevant content, a minor bit of non-earning text.

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 one-parameter, no-annotation tool with no output schema, the description supplies the return substance (par yields 1mo–30yr in percent), the date edge case, and the data origin. Exact field names/ordering in the response are left unspecified, which is the only real gap.

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%, and the schema already documents the YYYY-MM-DD format, the 1990-01-02 lower bound, the no-future-date rule, and the omit-for-latest behavior. The description adds nothing beyond the schema's own omit guidance, so the baseline 3 applies.

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 resource (US Treasury par yield curve), its unit and tenor range, and its scope ('for one date, or the latest if omitted'). That single-date scope implicitly separates it from the sibling yield_curve_history, but the sibling is never named, so the differentiation is left to inference.

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 clear guidance for the optional parameter ('omit for the latest') but says nothing about when to reach for this tool versus yield_curve_history. Usage is implied by the one-date scope rather than stated.

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