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

With no annotations present, the description carries the full burden and largely does: it discloses that the tool is paid at $0.002 USDC on Base or Solana, that no account or API key is needed, that failed calls are not charged, and that the underlying data is DefiLlama. The one gap is the return shape (beyond the three named metrics) and whether a protocol with no pools returns an error or an empty set.

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?

Six short fragments, each carrying distinct information, with the cost caveat front-loaded as 'Paid.' Nothing is redundant and the price, scope, and data source are all packed into two lines.

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-required-parameter, three-optional-parameter read tool with no output schema, the definition covers scope, output metrics, data provenance, and payment terms well. The remaining shortfall is the absence of any stated failure mode for unknown protocol slugs or empty result sets, which matters for an agent deciding whether to retry.

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%, and all three parameters (sort, limit, min_tvl_usd) are documented with defaults directly in the schema. The description only echoes that APY and TVL are output dimensions, which lightly hints at the sort values but adds no filtering or format detail beyond the schema. Baseline 3 is appropriate.

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?

The description names a specific resource (yields for the vaneck-treasury-fund protocol) and enumerates the returned metrics: APY, TVL, and 7d APY change. It is not tautological and an agent can tell this apart from the buy_yields_chain_* and buy_yields_token_* families because the scope is a single protocol. It stops short of explicitly contrasting with the closest sibling, buy_yields_protocol_* for other protocols, leaving the agent to infer that the protocol slug is the differentiator.

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?

Usage is implied by the scope statement: call it when you want live pool yields for this specific protocol. However, the description never states when to prefer this over a chain-scoped query (buy_yields_chain_base), a token query (buy_yields_token_usdc), or the aggregate buy_yields_top. No exclusions or prerequisites beyond the payment mechanics are given.

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