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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so safety is covered. The description still adds substantial behavior beyond them: partial-failure semantics (`sources_failed`, section null), total-failure as 503 not charged, null-vs-missing distinctions (`not_configured`), latency profile (0.2 s cache, ~30 s slow feed), price and free-tier quota. It omits little, but the dollar-index caveat and licensing notes are the main extra value rather than core call-shaping information.

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?

Front-loaded with the use case and the sibling exclusion before the return-shape details, and every clause carries information. It is dense — pricing, quota, latency, licensing and a docs URL in one paragraph — but nothing is redundant enough to cut without losing an agent-relevant fact.

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 zero-param aggregator with an output schema, the description covers sources, per-section metadata, null/failure encodings, latency, cost and quota. Nothing an agent needs in order to decide to call it, or to interpret a partial response, is missing.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; the baseline for a no-param tool applies. No misleading hints about inputs are given.

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 (macro rates backdrop: Treasury yields, SOFR/EFFR, FX, oil, gas) and a concrete scope ('in one call'), and explicitly contrasts itself with the sibling treasury_yield_curve for past-date curves. An agent can distinguish it from get_fx_rates, get_live_fx_rates, or treasury_yield_curve without opening any schema.

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 an explicit trigger ('Use when an agent needs the rates backdrop before a market decision') and names the alternative with the condition that selects it ('For the Treasury curve on a past date use treasury_yield_curve'). It also states exclusions (VIX, equity indices, gold) so the agent knows when not to reach for it.

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