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

Annotations already mark the tool read-only, open-world, idempotent, and non-destructive. The description adds high-value behavioral details beyond those: null instead of zero TVL, 5-minute caching, x402 payment mechanics on Base, unpaid calls returning a payment challenge, and no settlement on empty data. This is rich, non-redundant disclosure.

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 dense but every sentence carries operational value: purpose, filters, use cases, null handling, caching, cost, payment failure behavior, and the HTTP equivalent. It front-loads the core function and keeps the details organized without fluff.

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?

Even though there is no output schema, the description enumerates the returned fields, explains the null-vs-zero convention, and covers caching, cost, payment challenges, and failure semantics. For a paid, externally sourced tool with no output schema, this is enough for an agent to call it and interpret results.

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% and every parameter already has a clear description with examples. The tool description reinforces that filtering is by chain, category, or name substring, but it doesn't add meaningful per-parameter semantics beyond the schema, so the 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 action and resource: ranks DeFi protocols by TVL from DefiLlama, with explicit filter dimensions (chain, category, name substring) and return fields. The description also distinguishes it from the protocol-detail sibling by noting it can resolve the slug that the detail tool needs.

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 use cases: sizing a protocol, finding the biggest venues on a chain, and resolving slugs for the protocol-detail tool. It doesn't enumerate when-not-to-use conditions against all siblings, but the context and naming are enough to guide selection.

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