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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond that: cost ('Price: free'), error semantics (isError for invalid input or upstream failure, not charged), and the exact row fields returned.

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-loads the core definition, then examples, then when-to-use, pricing, and errors. Information-dense with little waste, though the enumerated row fields and category list border on schema duplication.

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?

Given an existing output schema and full annotations, the description still contributes data provenance, pricing, and error behavior, and covers filtering and ranking semantics. Nothing an agent needs to select and invoke 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 all five parameters are already documented in the schema with defaults, ranges, and enum values. The description adds only category examples ('lending, DEX, liquid staking, bridges, perps') that largely overlap the schema's own examples, so 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?

States a specific verb (rank), resource (DeFi protocols), the ranking basis (TVL or 1d/7d change), and the data source (DefiLlama, ~6,000 protocols). It explicitly distinguishes itself from the closest sibling by noting 'for one protocol in depth use defi_protocol'.

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?

Provides explicit when-to-use guidance with concrete example queries ('biggest lending protocols on Base', 'fastest growing DEXes this week') and names the alternative tool (defi_protocol) for the in-depth single-protocol case.

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