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

Beyond the readOnlyHint/openWorldHint annotations, it discloses that the result is signed by the service's on-chain delegated key, carries a verifiable receipt, and is explicitly data rather than instructions. These are exactly the trust and provenance details an agent cannot get from structured fields.

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 core behavior and the pairPrice routing are front-loaded and waste-free, and the return shape is included compactly. The service-identity and provenance sentences are justified but make it denser than strictly minimal.

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?

For a no-parameter, read-only price tool with no output schema, the definition supplies source pair, pinning semantics, provenance/signing behavior, and even the return shape ({ bnbUsd, pair, blockPinned }). Nothing an agent needs to call it 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% with a single optional block parameter whose enum values are already documented. The phrase "pinned to one block" and the stated default (finalized) merely restate what the schema provides, so the baseline 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 description names a specific resource and scope: "BNB in USDT from the PancakeSwap V2 WBNB/USDT pair, pinned to one block," and explicitly routes spot-price lookups elsewhere ("Spot price: see pairPrice"). An agent can distinguish it from siblings like pairPrice and blockNumber without opening any 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 explicitly provides an alternative for the adjacent use case ("Spot price: see pairPrice"), which is real routing guidance. It does not, however, say anything about when to pin to a specific block value versus the default, leaving that choice to inference.

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