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

With no annotations, the description carries the full burden. It does disclose meaningful behavior: the DefiLlama data source and the paid x402 model at 0.002 USDC per call, which is valuable for planning. It does not state that this is a read-only, idempotent lookup, nor anything about upstream caching or data freshness.

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?

Two short sentences, front-loaded with the core capability and followed by the cost model. Nothing redundant; the source and pricing each earn their place.

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?

For a simple read lookup with three optional parameters and no output schema, the description covers source, two query modes, and payment cost. Return shape (ranking fields, ordering) is not described, but it is largely self-evident from the stated purpose.

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 67%, and the description only indirectly touches the parameters: 'single chain' maps to chain, 'ranking' to limit's default of 20, and the per-call payment to paymentProof. The mechanics of paymentProof and the limit's max of 100 are left entirely to the schema, so the description adds only marginal meaning.

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 and resource: a TVL ranking of blockchains sourced from DefiLlama, or the TVL of one chain. The 'blockchains' scope implicitly separates it from the sibling protocol_tvl, but that differentiation is never made explicit.

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 two modes (ranking vs single chain) are implied by whether a chain is supplied, which is a reasonable usage signal. However, there is no explicit when-to-use guidance, no statement of when to prefer protocol_tvl, and no mention of the first-call-402 pattern in the description itself (only in the schema).

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