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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, but the description adds substantial behavioral context beyond those: the $0.005 USDC cost per call, the unpaid-call payment challenge response, the 'no data costs nothing' policy, and the null-TVL handling (excluded from total rather than zero). This fully discloses the tool's operational quirks, which is exactly what an agent needs to handle edge cases.

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 a single paragraph with multiple sentences, but each sentence earns its place: purpose, use case, null handling, cost/payment, and equivalent HTTP route. It is front-loaded with the core purpose and progressively adds operational details. It is not overly verbose for the amount of critical information it conveys.

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, the description must convey the return shape, and it does: it lists the key fields (chain, native token symbol, EVM chain id, summed cross-chain total) and the ranking order. It also covers null behavior, cost, and payment edge cases. While it does not specify exact field names or response structure, it provides sufficient context for an agent to understand what to expect and how to handle non-data responses.

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%, with both parameters (limit and search) already described in the input schema. The description does not add any parameter-specific meaning beyond what the schema provides; it focuses on output and cost. Given the high schema coverage, a baseline of 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 opens with a specific verb and resource: 'Total value locked per blockchain from DefiLlama, ranked high to low, with each chain's native token symbol and EVM chain id plus the summed cross-chain total.' This clearly differentiates it from siblings like defi_protocols (protocol TVL) and defi_yields (yields) by focusing on chains. The inclusion of concrete output elements (token symbol, EVM chain id, summed total) makes the tool's purpose unmistakable.

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?

It explicitly states two use cases: 'Use it to compare chains by capital deployed or to check where a chain sits.' It also provides operational guidance on cost and payment behavior. However, it does not mention any alternative tools or when not to use it, though the tool is distinct enough among siblings that this omission is minor.

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