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

With no annotations, the description carries the full behavioral burden and does so unusually well: it discloses the exact cost ($0.001 USDC), that failures (400/404) are never charged, that unestablished fields are returned as the literal string "unknown", and that the server holds no wallet and only returns 402 payment requirements for the agent to settle externally. An agent knows the cost, the failure cost profile, and the full retry flow 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?

It is front-loaded with the core question and the return fields, which is good, but the middle and end are dense run-on sentences and the payment mechanics are restated (no wallet, never pays, pay-and-retry) with overlap. Shorter phrasing would carry the same information.

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 must describe returns, and it does: the field list, per-field source citations and licenses, and the "unknown" sentinel for unestablished fields. Combined with error semantics and the payment flow, an agent has everything needed to invoke the tool and complete the paid call.

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%, so the schema already documents chain (slug/name/CAIP-2, with example), symbol, and address, including the symbol-or-address fallback. The description adds no parameter-level detail beyond what the schema provides, so the baseline of 3 applies.

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 question states a specific resource and the exact fields returned (symbol, name, decimals, contract address, issuer) for a stablecoin on a given chain, which is far more than a tautology. It also scopes the dataset (USDC, EURC, USDT, PYUSD, DAI on /v1/chain-covered chains), but it never names a sibling tool to contrast against, so differentiation from get_provider or stablecoin_rails is left to inference.

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 gives usable context: paid lookup, tokens must exist in the dataset, malformed input and misses return 400/404, and payment is completed by retrying the returned URL. However, it never states when an agent should choose this over the sibling tools (e.g. get_chain or stablecoin_rails), so the routing guidance is only implied.

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