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

Goes well beyond the annotations: it discloses output truncation for strings over 1,000 chars (e.g. on-chain SVG), 422-uncharged for nonexistent tokens, metadataError for unreachable metadata, the ipfs.io gateway path, and the $0.01/call price with a 25-call free tier. The note that repeats are charged is consistent with idempotentHint=false and explains the cost model annotations cannot express.

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 capability and its distinguishing scope are front-loaded, then behavior, error cases, example, and pricing in a sensible order. It is dense and the pricing/cost sentence is long, but no sentence is filler.

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 carries the return contract — it names the returned fields, the truncation rule, and the metadataError signal. Combined with the error and pricing notes, an agent has everything needed to call and interpret this tool.

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; the description adds a concrete worked example (contract=0xC364...FE88, tokenId=1) that fixes the expected address and token-id format for call construction. It does not add further constraints beyond that, so it lands just above baseline.

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?

States a specific verb and resource — reads the tokenURI and the resolved JSON metadata (name, description, image, attributes) for one ERC-721 token id on Arbitrum One. It also names the sibling it is not (arb_nft_owner) and its chain-specific scope, so an agent can distinguish it from eth_/base_/op_/polygon_nft_metadata without opening schemas.

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?

"Use to show or check what an NFT is; for its owner use arb_nft_owner" gives an explicit when-to-use plus the routing alternative. It also names the supported metadata sources (data:, https, ipfs://) so an agent knows which tokens it can resolve.

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