defi_tvl

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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, and the description adds materially beyond them: cost ('free'), auth posture ('no API key, nothing signed or spent'), and explicit failure behavior ('Fails with an error message on an unknown symbol or an unreachable upstream source'). That failure-mode disclosure is exactly the kind of operational context an agent needs before calling.

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 core purpose, then cleanly sectioned into Use when / Not for / Returns / Example / Cost and failure. Every section earns its place, though the 'Example response' field list partially repeats the 'Returns:' enumeration, which is minor redundancy.

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?

There is no output schema, so the description correctly compensates by enumerating return fields (tvl, change_1h/1d/7d, chains[], category) and giving a concrete example response. Combined with the cost/auth/failure notes, an agent has everything needed to call and interpret 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% and the single parameter already documents 'Leave empty for top 10'. The description restates that behavior ('Returns top 10 or a specific protocol') but adds no new syntax, format, or constraint detail. Baseline 3 applies when the schema carries the parameter semantics.

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+resource ('DeFi protocol Total Value Locked from DeFiLlama') and immediately defines scope: top 10 or a single named protocol. This is distinguishable from every sibling (yield_scanner, dune_query, token_market_data) without opening a 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?

Explicit 'Use when' clause names the two valid scenarios (single protocol TVL, comparing top protocols), and the 'Not for' clause routes to named alternatives (yield_scanner for best yield, dune_query for revenue/custom metrics). When-to-use and when-not-to-use are both present with the alternatives spelled out.

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