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

Even with strong annotations (readOnlyHint, openWorldHint, idempotentHint, destructiveHint=false), the description adds valuable behavioral context: null TVL is excluded from totals rather than counted as zero, each call costs $0.005 USDC, unpaid calls return a payment challenge, and no-data calls are never settled. This goes well beyond what annotations provide.

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?

The description is front-loaded with the core resource definition and ranking behavior, then adds use case, null handling, payment details, and an HTTP equivalent. Every sentence carries useful, non-redundant information with no filler.

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 output schema present, the description carries the burden of explaining what the tool returns, and it does so thoroughly: chain TVL, ranking order, token symbol, EVM chain id, cross-chain total, and null handling. Payment behavior and route equivalence further complete the picture for an agent deciding whether and how to call this tool.

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 the input schema already fully documents both limit and search parameters. The description adds no parameter-specific details beyond the schema, such as search case-sensitivity or default limit behavior, but it is not required to compensate for any schema gap here.

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 clearly states that this tool returns total value locked per blockchain from DefiLlama, ranked high to low, and lists the key returned fields (native token symbol, EVM chain id, cross-chain total). It is immediately distinguishable from sibling tools like defi_protocols or defi_yields by focusing specifically on chain-level TVL ranking.

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 description gives explicit use cases: compare chains by capital deployed or check where a chain sits in the ranking. It does not name alternative tools or state when not to use it, but the context is clear enough for an agent to select it for chain-level TVL comparisons.

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