Has this rate held?

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

Annotations already declare readOnly, idempotent, non-destructive, so the safety profile is covered; the description adds genuine value by disclosing the interpretation hazard that a short `observations` series should not be read as stability. It does not cover cost, rate limits, or pagination, so it is useful context rather than complete disclosure.

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 sentences, each doing distinct work: what it returns, why it beats a live rate, and a caveat on sparse data. The most actionable instruction (call before acting on a high rate) is front-loaded in the middle of the text without preamble.

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 carries the burden of describing returns and does so concretely (daily series plus min/median/max/volatility and an `observations` count). For a two-parameter read-only tool, nothing an agent needs to call it correctly 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?

Schema description coverage is 100%, with `pool` even documenting its source in list_base_yields and list_lending_vaults, so the baseline is 3. The description adds no further syntax or format detail for `days` or `pool` beyond what the schema already states.

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 (daily APY and TVL history for one market) plus the derived statistics returned (min, median, max, volatility), which makes its role unambiguous. It also carves out its niche against the live-rate siblings (list_base_yields / best_yield) by framing itself as the tool that answers what 'a live rate cannot.'

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 a clear triggering condition: 'Call it before acting on any unusually high rate,' and explains the question it answers (typical vs. spike). It does not explicitly name an alternative sibling or state a when-not case, so it stops short of full routing guidance.

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