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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuine value by disclosing the payload shape (previous session, change per tenor, 2s10s spread), which matters since no output schema exists. It says nothing about defaults, data source, or what happens when 'country' is unsupported and 'history' is non-zero.

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?

A single tightly packed sentence with the most important content (what the curve contains) front-loaded and zero filler. It is a fragment rather than a sentence, but nothing is wasted.

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?

With no output schema, the description competently covers the return payload, which is the main gap it needed to fill. However, for a 3-parameter tool with a wide-range 'history' argument and a country selector, leaving all parameter behavior unexplained means an agent cannot confidently configure a call.

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 only 33%: 'date' has a format hint, but 'country' (default 'us') and especially 'history' (0-250) are undocumented in both schema and description. The most consequential open question — whether 'history' returns N days of curves — is left entirely unaddressed despite being the obvious intent.

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?

Names a specific resource (daily par yield curve) and enumerates what it returns: previous session values, per-tenor change, and the 2s10s spread. That distinguishes it from macro_policy_rates and macro_latest_releases in domain terms, though it never explicitly routes against those siblings.

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?

There is no statement of when to use this versus macro_policy_rates, macro_history, or macro_latest, and no prerequisites or exclusions. The agent must infer from the name alone that this is the curve-specific source.

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