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

Annotations cover the safety profile, but the description adds substantial behavioral context beyond them: supported URI schemes, IPFS resolution through ipfs.io, truncation of strings over 1,000 characters, 422 handling for nonexistent tokens, metadataError reporting for unreachable metadata, pricing, and that repeat calls are charged. No contradiction with readOnlyHint/destructiveHint.

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 description is front-loaded with the core purpose and return shape, then adds only operationally relevant details: URI support, truncation, failure behavior, sibling routing, pricing, and mutation safety. Every sentence contributes to correct invocation or interpretation.

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, but the description explains the return values (token URI plus JSON fields), truncation behavior, metadataError, and the 422 case. Combined with full parameter coverage and rich annotations, an agent has enough to call and interpret this tool correctly.

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 both parameters are already documented as contract address and token id. The description adds a concrete example and confirms tokenURI behavior, but it does not add syntax or validation rules beyond the schema, so baseline 3 is appropriate.

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 states a specific verb and resource: read the token URI and pointed-to JSON metadata for one ERC-721 token id on Base. It also explicitly distinguishes itself from the sibling base_nft_owner, making the scope unambiguous.

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 an explicit use case ('Use to show or check what an NFT is') and names the alternative for a different need ('for its owner use base_nft_owner'). This is clear when/when-not guidance, not mere implied usage.

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