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

Annotations already declare read-only/idempotent/non-destructive, but the description adds far more: data is cached DefiLlama data refreshed every few hours and never live, `as_of` exposes staleness, 422 vs 503 error semantics, neither error is billed, typical latency under 1s, and pricing/free-tier limits. This is exactly the extra context the annotations cannot carry.

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 purpose and the alternative tool, then behavior, then inputs, then operational constraints. It is dense and every sentence carries information, though the leading "chainpeek:" tag and the repeated mention of cached DefiLlama data are mildly redundant against the title.

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?

An output schema exists, yet the description still sketches the return shape, and it covers staleness, error codes, billing, rate limits and a docs link. Nothing an agent needs to decide or call correctly is missing.

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%, so the baseline is 3 and the schema already documents coin, chain and limit in detail. The description nevertheless adds genuine meaning beyond the schema by spelling out the combination semantics (one, both, or neither) that govern how those fields interact.

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 opening sentence gives a specific verb+resource ("Get stablecoin supply by coin and chain") and immediately names the sibling it must not be confused with (check_stablecoin_peg for peg status). An agent can route correctly without opening either 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?

It states the alternative tool and the condition that selects it, and it explicitly resolves the parameter-combination question ("give one, both or neither") plus what each combination returns (a coin's chains, a chain's coins, or the largest coins and chains). No usage inference is required.

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