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

Beyond the readOnlyHint/openWorldHint annotations, the description discloses three things an agent cannot infer: IPFS/Arweave URIs are resolved to gateway URLs, output is deterministic (no LLM), and the call is paid ($0.007 USDC on Base via x402, payment passed in _meta["x402/payment"]). The payment prerequisite in particular is critical and would otherwise cause silent failures.

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 a two-word purpose followed by capability, chain scope, resolution behavior, and payment terms. The inline example output is long but earns its place because no output schema exists. The pricing sentence is dense but functional rather than redundant.

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 three simple parameters, full schema coverage, and no output schema, the description covers the essentials: return shape via example, URI resolution, chain options, and payment mechanics. It stops short of stating failure modes (non-contract address, unreachable IPFS, unsupported token standard) or whether metadata is cached.

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 contract, tokenId and chain are already documented, including the base default. The description only echoes the chain list and shows tokenId as a string in the example; it adds no format or constraint details beyond the schema, 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 the resource (NFT metadata) and precisely enumerates what is returned: tokenURI plus resolved JSON fields (name, description, image, attributes) for ERC-721/ERC-1155 tokens on four named chains. It is far more specific than a title restatement, but it never names the closest sibling (nft_owner) to draw the metadata-vs-ownership boundary.

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 scopes applicability by token standard (ERC-721/ERC-1155) and by supported chains, which implicitly tells the agent when the tool is valid. However, there is no explicit when-to-use statement, no exclusion, and no pointer to an alternative such as nft_owner or contract_abi.

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