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

Annotations already declare readOnlyHint=true and openWorldHint=false, and the description is consistent with both. It adds value beyond them by disclosing the ranking methodology (risk-adjusted APY), the result cardinality (top 5), the chain coverage (all chains), and pricing, though it says nothing about caching, freshness, or rate limits.

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 short sentences, zero waste, with the free/cost signal front-loaded and the sibling pointer last. Every clause earns its place by either scoping the result or routing the agent.

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 input schema and no output schema, the description does the necessary work by naming the returned fields (APY, TVL, risk level) and the ranking basis. Minor gap: it does not characterize freshness/update cadence or the exact result envelope, which matters for a data-feed tool relying on prose alone.

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 is 4. The description correctly conveys that scope (all chains, no filter argument), which is the relevant semantic fact for a no-arg tool.

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 and scope: 'Top 5 DeFi yields across all chains ranked by risk-adjusted APY', plus the fields returned (APY, TVL, risk level). It explicitly names the sibling it is not — lookup_yields — and the axis on which they differ (filtering by chain/token).

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?

The FREE marker versus lookup_yields' $0.002 cost plus its 'filters by chain/token' capability gives the agent a clear routing decision: free fixed top-5 here, paid filtered queries there. It stops short of an explicit 'use this when you do not need filtering' exclusion, so it is strong but not fully spelled out.

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