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

Beyond the readOnly/openWorld annotations it discloses data source (DefiLlama), window cap (365 days), billing model ($0.01/call via x402 USDC or card key, first 25 free, failed calls free) and explicitly explains why repeats are not free — which reconciles with idempotentHint=false. It also notes the tool only reads/computes and changes nothing, consistent with destructiveHint=false.

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?

One dense paragraph that front-loads what is returned, then usage, then pricing. All sentences carry information, though the 'Not investment advice' clause is peripheral and the pricing/auth tail could be trimmed.

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?

There is no output schema, but the description enumerates the return payload (daily APY base and reward, TVL, average/min/max/latest APY) so the agent knows what comes back. Combined with the window limit, source and cost model, nothing needed 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%, so both `pool` (UUID or URL) and `days` (1-365, default 30) are already documented in the schema. The description only restates the pool-id-or-URL form and adds a sample UUID; it adds no syntax or edge-case meaning beyond that, so 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 verb and resource: 'Daily APY and TVL history of one DeFi pool', and pins the scope to a single pool id. It explicitly routes pool discovery to the sibling /defi/yields endpoint, so an agent can separate it from defi_yields or liquidity_pool_audit without opening a 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 a concrete decision context: 'Use to check whether a yield is steady or a short spike before an agent deposits', and names the source of the pool identifier. It does not state explicit when-not conditions or name a direct alternative for the history question, so it stops short of a 5.

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