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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower. The description still adds real behavioral context: pricing ('free') and error semantics ('returns isError... not charged'), plus what the two modes return. It does not discuss pagination or rate limits, but the mode behavior and charge model are useful additions.

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-loaded with the dual behavior before the DefiLlama attribution and usage routing. Dense and mostly waste-free, though the attribution line ('DefiLlama chain TVL') is mildly redundant with the opening sentence.

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?

Covers the two operating modes, the parameters that switch them, pricing, and error behavior, and an output schema exists so return values need no explanation. An agent has everything needed to invoke this correctly.

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 coverage is 100%, so baseline is 3. The description goes beyond it by mapping the 'chain' parameter to an output mode, explaining that 'days' yields up to 365 days of history plus 7d/30d/90d change metrics, and clarifying the ranking scope. Only 'limit' semantics are left entirely to the schema.

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: total value locked per chain, ranked, or a single chain's daily history. It explicitly distinguishes itself from defi_rankings (protocols) and from other TVL tools, so an agent can pick it without opening the 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 explicit mode-selection rules ('Without "chain": ranking... With "chain": daily TVL history') and names the alternative for a different use case ('for protocols use defi_rankings'). Nothing about when to use it versus alternatives is left to inference.

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