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

Beyond the readOnly/openWorld annotations, it discloses the cost model ($0.002 USDC per successful call, x402 on Base/Solana/Arc), that failed calls are not charged, and that attribution to DefiLlama is expected. Payment mechanics and failure-charging behavior are exactly the kind of operational detail annotations cannot convey.

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 data scope followed by mode behavior, attribution, disclaimer, and pricing. Every sentence carries information, though 'Information only, not financial advice' is boilerplate that could be trimmed without losing call-relevant meaning.

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 one optional parameter, an output schema, and read-only annotations, the definition covers what is returned, the default scope, and the cost of a call. It omits how to retrieve stablecoins beyond the top 50 (pagination or ranking criteria), which is the one gap an agent might hit.

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% and the single optional parameter is documented in the schema, so the baseline is 3. The description adds real semantic value by specifying the default result set (the 50 largest) when symbol is omitted, which the schema does not state.

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 names the concrete resource (stablecoins tracked by DefiLlama) and enumerates the returned dimensions: circulating supply, peg type and mechanism, price, and supported chains. That is enough for an agent to separate it from defi_tvl, defi_chains, or crypto_price, though no sibling is named explicitly.

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?

'With symbol, that coin; without it the 50 largest' gives clear mode-selection guidance between the two call patterns. It stops short of telling the agent when to prefer this over crypto_price (live quotes) or token_metadata (token details), so usage is implied rather than routed.

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